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Hi, all,
This is too much to just change in the main entry. May I have some comments so I can fix the proposed text up? My own comments are in [bracketed italics] 2B removed later. (I know there is an !-- Invisible Note to editors -- mechanism, but these comments should be seen on the TalkPage. I'll hassle getting them out later.)
PROPOSED TEXT
Individual silver halide crystals suspended in a film emulsion aggregate into clumps ("grains") of random size. [Grains are not as regular and orderly as the crystals which lie at their heart, and at the heart of the energy storage mechanism that makes it possible to store and later develop a latent image] Even when these are not individually resolved in an image, a texture ("graininess") remains. Higher film speed brings more graininess. [nice direct statement from original more or less] Fine-grain stock, such as film used for portraiture or copying, is "slow", meaning that the amount of light used to expose it must be high or the shutter must be open longer. Fast films, used for shooting in poor light or for shooting fast motion, produce a grainy image. [Easily grasped contrast of different practical situations, also from original, more or less]
Since each grain of silver halide develops in an all-or-nothing way, photographic images actually consist of a mosaic of developed and undeveloped areas. In this sense, film is a threshold detector rather than a linear detector. [This is a delightful insight to present, at a time when so many of us are making the historic transition from "analog" to "digital". However, it didn't have enough of a "compare and contrast" discussion to clarify differences between the two ways of conceptualizing film's function.] If the subject has an edge between light and darkness and that edge falls on a grain, the result will be an area that is all light or all shadow. Fine gradations of grayness are also quantized, so that graininess interferes with the perception of shape from shading as well as with object contours (edges). [As the brain imposes structure on sensation to achieve perception, "shape from shading" has emerged in recent decades as an important mechanism of shape encoding from surfaces, just as contours and their elaboration in the brain is an important mechanism of shape encoding from edges, and of figure/background segmentation. Also, it makes for beautiful b/w photos :-) ] Photographers sometimes exploit film's quantization with high-contrast derivatives ("orthos") that really are only black or white, [These are typically made with photolithography film like Kodalith, hence the name. I put this in to be sure readers understand that it's hard to get even grainy shots to lose their grey-ness, unless special steps are taken. Perhaps it can be dropped to keep everything brief. Opinions? ] but the issue of quantization is moot in most photos, because grains are random in size, overlap, and are not individually resolved in the image. Under such typical circumstances, slow films have higher contrast, and faster films have not only lower contrast, but a much longer gray scale, beloved of available light photographers in journalism and movie making. [There was a problem in the original on this point. Maybe you can say it better, but we need some kind of clarification. An ASA 400 b/w film has what they call a "longer grey scale" than an ASA 25 film. Subjectively, I've always thought the grays of fast film "looked nicer", but technically it means that the negative film goes deeper into highlights before blocking/saturating, and it can throw a few grains into shadows before falling to baseline density at low image intensity.]
Original: "Fast films are also relatively contrasty, for the same reason. That is, an area of the image will consist of bright areas and dark ones with few transitional areas of midtones." This statement is misleading at best. Slow films have a higher gamma.
END proposed text.
Please don't clobber me. If there are better ways to handle a suggested revision, just say. As for the revision itself, entries on technology are of necessity always a work in progress, so this won't be the last change, and not every change has to be made.
Thanks!
Jerry-va
17:09, 27 February 2006 (UTC)
Does anyone know how films speed and the ISO ratings relate to digitalo cameras? I think this would be useful to add.
BEGIN remark Quote: "However, this loss is visible as image noise rather than grain." As someone from the area of digital image processing research I find this a completely non-technical and unsupportable statement. Maybe I am overlooking something. Please define the difference. If analog graininess and digital snow look different because of the square raster, I would understand it. However, from some distance artificial graininess in digital images cannot be discerned from the example given. Note that the figure on the page is also digital, with square pixels.
END remark —Preceding unsigned comment added by 94.212.221.215 ( talk) 22:52, 5 August 2010 (UTC)
A while ago, I removed Delta 3200 from the chart, and today an anonymous user, in what I assume to be a well-meaning edit, added it back (at 3200). The reason that I removed it is that Delta 3200 does not have a true ISO speed of 3200; according to the data sheet, the true ISO speed is 1000. Shooting it at the recommended speed of 3200 is actually " pushing" the film, and will result in higher contrast and less shadow detail than if it were shot at the ISO speed. For this reason, I don't think it's appropriate to list it on the chart. Listing it under 3200 is inaccurate, and listing it under 1000 would be confusing without a lengthy explanation. Similar arguments apply to Kodak's Tmax P3200. -- Coneslayer 18:00, 2005 Apr 17 (UTC)
I have edited the article slightly to remove the common misconception that the f-number is equal to the ratio of the focal length to the aperture diameter. It is not. The f-number is equal to the ratio of the focal length to the diameter of the entrance pupil of the lens. The latter is proportional to the diameter of the aperture. It is true that doubling the f-number halves the diameter of the aperture but it is not true that the aperture diameter is equal to the focal length divided by the f-number.-- Srleffler 04:29, 14 February 2006 (UTC)
The description of ISO film speed method refers only to that for still colour negative film. Wouldn't it be more thorough to mention the ISO 6 method for B&W film; why there is a difference between the methods for B&W and colour film; why chromogenic B&W film doesn't quite fit with either; and the existence of a separate standard for colour reversal film? It might also be worth mentioning that there is no ISO for motion picture colour negative film. I would be happy to write the aditional material, as I have all the relevant standards.
-- Helen Bach 15:50, 31 March 2007 (UTC)
Helen, I realize you wrote this 3-1/2 years ago, but I can't imagine why ECN-2 (and equivalent) motion picture films wouldn't have an identical standard to C-41 (and equivalent). My can of 5201 (Kodak Vision 2 50D) does only have EI ratings, but I would assume that is only because that Kodak assumes that Cinematographers will run tests on their filmstocks. This is similar to the practice of B&W photographers coming up with their own EIs for their favorite stocks, such as an EI of 320 for Kodak Tri-X 5063, or Portra 400NC. ISOGuru ( talk) —Preceding undated comment added 00:45, 11 November 2010 (UTC).
Images of a flower taken at ISO 100 and ISO 1600 on a Canon 400D digital camera. Both images were shot under similar lighting conditions, varying only the ISO setting and shutter speed.
I can understand how they were shot under similar lighting conditions, but the illustration is incredibly fallacious, as the ISO 1600 shot would be overexposed compared to ISO 100. Shutter speed would need to be 16 times faster to achieve the same exposure, ie. 1/5600. This is a 2/3 stop of a difference, and that's assuming that the 1/4000th setting (fastest on that camera) is exposing correctly. Tests (in magazines) show that even shutters in professional cameras overexpose by as much as a whole stop at their highest speed, the problem is even more pronounced in amateur cameras (such as 400D). This test would be a good candidate to be repeated (possibly with the same camera), at shutter speeds of 1/100th and 1/1600th or slower. —The preceding unsigned comment was added by 217.153.194.14 ( talk) 21:01, August 23, 2007 (UTC)
I have a Sony HVR-A1J HDV camcorder with a 1/3" CMOS sensor which can be used as a still camera with images saved to a memory stick. The sensitivity of the camera is defined as: 7 lux at +18db with a normal shutter. Let's take this apart: 7 lux is a little less than one foot candle - sounds great, but that 18db is telling us that the noise level is going to be horrendous. Normal shutter probably refers to something between 1/30 and 1/48 second (25 or 30 frames/sec - this camera doesn't actually scan fields). If we move the gain back down to 0 db, sensitivity is more likely to be in the 400 to 1000 lux range. (Well you can do the math to get an exact number. I'm not going to bother.) This actually puts the camera in a fairly standard professional video camera sensitivity range - ISO 160 (or using our old friend Ektachrome 160 in the Bolex), where you can push the film in processing or turn up the gain as needed.
What would be muchly appreciated is a Wikipedia entry that incorporates a cross reference table comparing all these different units of sensitivity to each other. Competitive manufacturers product literature rarely uses the same standards so very little makes sense - like mixing RMS and EIA watts! -- Mccainre ( talk) 07:32, 7 January 2008 (UTC)
Lux (meter candles) is also used to define ISO speed. And, since there are 10.76 candles at a meter (therefore 10.76 meter candles) (lux) as a candle at one foot ( 1 foot candle), that's only 2/3 of a footcandle.
According to a thread I read on Photo.net, the clearest explanation of ISO by the way, I've read thusfar, defines ASA/ISO as "0.8/the speed point in meter candle seconds. The speed poin is many times. 0.1 density units over gross fog. [base fog?]" and, as an example: "An ASA/ISO 800 film requires an exposure of 0.8/800 = 1/1000 of a meter candle second[. . .]" This is WITHOUT A LENS. So you'd have to compensate for light loss based on T-- (not F/-) stops. ISO and foot- or meter- candles are related. ISOGuru ( talk) 00:56, 11 November 2010 (UTC)
According to light meter, the ISO film speed S is given by S=Kn^2/Lt, where L is the luminance of a medium-brightness area (candela/m^2), n the aperture number, K a constant (usually between 12 and 14), and t is the shutter speed. Usually, medium brightness is taken to be an 18% reflective card. However, this doesn't say anything about the headroom. Should a sensor with a given ISO number be at exactly 18% of saturation for a given luminance L? Or is there a standard amount of headroom? I've searched a bit and I found numbers of 106%, 170%, and 141% for the saturation level. What does the ISO document say about it? This information is missing. See e.g. [1], [2], [3]. Han-Kwang ( t) 15:21, 10 October 2007 (UTC)
(copied from Talk:Light meter) I see, so the equation n^2/t = LS/K is a simply a definition of what the reading that a light meter should produce for a given luminance, even though K is somewhat variable. But as a photographer, of course I would want to know how much headroom I will get if I point the light meter at a 18% card. As you say, officially the saturation level should be 141% (1/2 stop above 100%), but in practice YMMV (e.g. my digital compact camera seems to aim for 18/100 rather than 18/141). Maybe this subject really belongs on film speed, where I also asked this question. Anyway, I think the focal plane exposure is given by H=pi L t/4 n^2 (for objects far away from the lens), so Ssat = 78/Hs = 312 n^2/ (pi*Lsat*t) where Lsat is the luminosity that just saturates the sensor. I guess that 78 comes from 100*pi/4, so Ssat=100 n^2/(Lsat*t), which seems to be an elegant equation -- would it be appropriate to mention on film speed? Han-Kwang ( t) 23:43, 10 October 2007 (UTC)
(copied from
Talk:Light meter) I've posted something on
Talk: film speed. Now that I have read Dicklyon's posts here I see that my post there is a re-write of the end of his previous post - ie that the 78 factor in the Ssat formula comes from 141/18. The formula for focal plane exposure used in 12232 (Eq 2) takes flare exposure (Hf), cos^4 loss, lens transmission factor (T) and vignettng factor (v) into account. The pi/4 combines with the other losses (T v cos^4theta, with Hf << H) to produce 65/100 (which is 0.83 pi / 4), so the formula for arithmetic mean focal plane exposure is 65 La t / (100 A^2) where La is the arithmetic mean scene luminance and A is your N. On axis the focal plane exposure would be 0.88 pi L t / (4 A^2).
Helen Bach
22:47, 11 October 2007 (UTC)
(unindent) To Helen: 1) OK for the vignetting, but after some thinking I don't see why it is cos^4 rather than cos^2. One cos(theta) comes from the angle of incidence onto the lens, and the other cos(theta) from the angle of incidence onto the focal plane. Derivation:
D ,-| b o |,-' --------------------+----- ,-' | f ,-' o/cos(theta),-' ,-' spatial angle dOmega ,-' |,-' a |
a is a small surface with a luminance L; the surface has an intensity I=L a cos(theta) [candela] and sees the lens (at a distance o>>f) with a spatial angle dΩ=D^4 cos(theta) pi/4 o^2 . The flux as captured by the lens is
The image in the focal plane has a surface b=af^2/o^2. The illuminance E at the focal plane is then
With D=f/N,
Of course, you can add extra factors for vignetting v(theta) and a lens transmission T,but that doesn't explain the cos^4.
2) and 3) - OK, that's the difference between gamma 2.2 and sRGB, but that's not going to be a big effect at 1 stop below JPG saturation.
4) It looks like (consumer) camera manufacturers are ignoring that part of the ISO standard.
To Dick: aha, 118/256 is 18.4% of saturation in gamma=2.2 and 18.0% in sRGB. (Are you sure it wasn't 18/255 by the way?) And then we are actually back to where I started: SOS rating S (100, 200, 400, 800, etc.) is equivalent to a ISO saturation speed, except that the SOS number refers to saturation of the output JPG image and the ISO number refers to saturation of the sensor.
If one of you can explain the cos^4 factor to me, I think it's time to expand the article.
Han-Kwang ( t) 07:16, 13 October 2007 (UTC)
How time flies. I'm still working on the draft I promised. Meanwhile, how about changing the arithmetic - logarithmic conversion formulae to the one implicit in the speed definitions given in ISO 6 and ISO 5800, and stated explicitly in ISO 2240; and the derived inverse?
This is the conversion method derived from the two speed definitions in each of ISO 6 and ISO 5800, and stated explicitly in ISO 2240: S° = 1+10 log S
This is the inverse of the above, which is not specifically mentioned in the Standards: S = 10^(S°/10) / 1.26
All base 10 logs.
Helen Bach 16:36, 10 October 2007 (UTC) —Preceding unsigned comment added by Helen Bach ( talk • contribs) 16:33, 10 October 2007 (UTC)
It is stated explicitly in ISO 2240, and can be arrived at by simple substitution in the speed formulae given in ISO 6 and ISO 5800. Its ancestry goes back further than that, but those are the three current standards. The relationship is based on the definitions of arithmetic and logarithmic speeds, not on a purely mathematical correlation between the integer pairs 100/21, 200/24 etc. Helen Bach 03:59, 11 October 2007 (UTC)
Will the formulae be changed? What happens next? I'm new to all this. By the way, which table in 12232 are you referring to? Thanks.
Helen Bach
22:11, 11 October 2007 (UTC)
I removed this:
Reasons:
Han-Kwang ( t) 00:19, 7 January 2008 (UTC)
I think the article would benefit from a photo comparison of different ISO settings. I like Dicklyon's suggestion to have a picture with something that moves against a steady background. It would be nice, though, if the picture had some aesthetic value as well when cropped (not scaled) to 250x150 px. Han-Kwang ( t) 09:40, 8 January 2008 (UTC)
Where does the information that the original Kodachrome was ASA 6 come from? I've read in some sources that it was 8 and in some that it was 10, but never 6. —Preceding unsigned comment added by 130.232.17.50 ( talk) 09:23, 6 May 2008 (UTC)
Since ASA was in flux before the 1950s, a speed of "6" in WWII does not necessarily correspond to a speed of "6" ASA today. While this wasn't the case with reversal, to be sure, ASA speeds for B&W were effectively doubled in the 1950s. I have no source to back this up, but I've seen it mentioned many many times by those knowledgeable in such things in Photography Fora on the internet. —Preceding unsigned comment added by ISOGuru ( talk • contribs) 23:52, 10 November 2010 (UTC)
Parts of the article seem to be written more to convince the reader that the author knows the subject than to explain the subject to the reader.
Could it be simplified - perhaps by adding more explanations and links? Perhaps by adding very short summaries to each section?
One thing I had problems with was "clipped or bloomed". To me they are not well defined terms. If it is standard terminology, it would be good to explain them, either here or in separate articles. Mlewan ( talk) 07:12, 31 May 2008 (UTC)
I'm an amateur who understands film sensitivity and was looking for an explanation about digital sensitivity. I do not pretend to understand the math or the formulae for either film or digital. From my perspective, what is missing in this article is a layperson's summary of what generates digital noise. The key is on "layperson". That will probably lead to a major simplification and result in long and endless debates about how much simplification is appropriate! I don't know the answer to that. but I do know that this article as it exists today (3 Feb 2009) is way over my head and provides me with no useful information.
Also, the eraser images above. For me, the blurring confuses the demonstration of noise. I do understand why the image is blurred. Showing two effects in one photo will lead to confusion among those who come here seeking info. Three shots would be a better demo. But make the slow shot at a reasonable speed that people would use for hand held. I believe that few point and shoot cameras would let one take a shot at 1/5th without some warning, and most users of DSLR would probably understand that 1/5th is too slow for hand held - even with vibration reduction. (Though I'd probably still push it and hope!) [[[Special:Contributions/207.236.137.2|207.236.137.2]] ( talk) 18:47, 3 February 2009 (UTC)Peter in Canada]
I am struggling with the relationship between "exposure index" and film "sensitivity". The exposure index section confuses me:
That description and the lengthy example that follows it seem more concerned with "arbitrary exposure compensation" than "film speed" calibration. I've got it into my head that:
Where am I going wrong? -- Redbobblehat ( talk) 22:43, 16 February 2009 (UTC)
As it stood prior to the 8 January 2010 edit by 75.118.66.209, the table agreed with ISO 12232:1998 for speeds up to 10,000; absent a persuasive argument to the contrary, I think we need to treat that standard as authoritative. Both ISO 12232:1998 and CIPA DC-004 2004 stop at 10,000. I don't have ISO 12232:2006, but if it gives speeds beyond 10,000, those values should be used; if not, we should defer to values given by camera manufacturers. ASA PH2.12-1961 (Table 2, which compared arithmetic and logarithmic parameters) showed a value of 12,500, and this table was included in Appendix 2 of ANSI PH3.49-1971; the table was not included in ISO 2720:1974. Because that value hasn't been repeated in almost 40 years, it's difficult to see it as controlling.
More often than not, standardization lags practice, and accordingly, standards often simply document practice. Canon and Nikon have stated the higher ISO speeds as they have, and absent solid authority to the contrary, those are the de facto values. The role of Wikipedia is to document, not advocate, and we simply can't arbitrarily replace a widely accepted value with one of our own, no matter how logical a particular editor may think it.
I agree with 75.118.66.209 that the ISO rounding is somewhat arbitrary, but it follows long-established practice, and in any event, ‘tis as ‘tis. Whether the rounding is “improper” is a matter of personal opinion. In theory, speeds progress in steps of the cube root of 2, and I suspect (but cannot document) that meter calibrations make that assumption; the notes to Table 2 of ASA PH2.12-1961 stated as much. But the notes to that table stated that the “exact” value of ASA 25 was 26.7 due to the arcane conversion between ASA logarithmic and arithmetic speeds. If that is still the case, insisting on “proper” values for every speed would lead to quite different from those to which we are accustomed. Because APEX never really caught on, I'm not sure that table is still meaningful; more recent standards (e.g., ISO 2720-1974) make no mention of it.
Absent an authoritative source, I'm not sure it's possible to determine the “exact” values for each speed. If indeed it were possible, insisting on “exact” values would require changing almost every value in the table. Given that speeds are rounded to the nearest 1/3 of an exposure step anyway, the quest for exact values seems pointless.
Accordingly, I've restored the ISO speeds to their previous values. If 75.118.66.209 can provide an authoritative source for the values he suggested, the matter is of course open to discussion; otherwise, I think he should refrain from further such edits before discussing the matter here. JeffConrad ( talk) 02:20, 11 January 2010 (UTC)
Despite repeated requests for sources, 75.118.66.209 insists on adding unsourced material that in some cases is essentially
original research (e.g., “higher speeds can be extrapolated”) and in other cases is unsupported personal opinion (e.g., “corrupted”). When material is challenged, the
burden of evidence is on the editor adding the material, and this editor defiantly refuses to provide any supporting material or even respond on the talk page. Accordingly, I've removed the unsourced material, in accordance with
WP:V.
JeffConrad (
talk)
20:44, 11 January 2010 (UTC)
I think most of us can work out progressions of speeds, but we cannot displace de facto standard values with our personal preferences. In any event, material like “If they called the values "100,000,000 and 500,000,000" that would make the numbers right too :-/ Learn some basic math. . .” is clearly inappropriate for an article, and it's difficult to see this as a good-faith edit. And the comment “Its on” seems an obvious challenge to an edit war. Accordingly, I suggest we treat this as vandalism, and I have so warned ISOguru. Anyone else?
JeffConrad (
talk)
As the article stands, it includes unsupported personal opinion that's at odds with de facto standard values. I think we should follow WP policy and insist that controversial matherial be supported, but I am not going to waste time in an edit war with ISOguru/75.118.66.209, who apparently sees no need for sources or discussion.
JeffConrad (
talk)
23:48, 11 January 2010 (UTC)
I've made some changes in attempt to satisfy ISOguru while keeping to what can be supported by reliable sources. ISO 12232:1998 does not specify a speed greater than 10,000, but the upper limit for Snoise 10,000 is given as 12,500, suggesting that ISO may have envisioned the progression that ISOguru claims. But this is speculation, and at present, the only devices with speeds greater than 10,000 have specified speeds using a power-of-2 progression that continues from the highest previously realized speed of 6400. Because these speeds are not given by ISO, they are ISO equivalent speeds, as the comment in the table already notes. Because values using the Canon/Nikon progression have actually been specified, I've restored those values to the table rather than speculate on what ISO intended or may eventually adopt. If another manufacturer announces a product with a speed using the progression that ISOguru proposes, I suggest we address it at that time by changing the entry to something like
I've tried to address ISOguru's issue in Note 3. Although there is some speculation, I've made it clear that such is the case. Without some speculation, the alternative progression cannot be addressed until we have a reliable source. Hopefully, this will be acceptable to all concerned.
I've removed references to “proper” value and “corrupted”, because these terms are non-NPOV, and accordingly have no place in a Wikipedia article. If ISOguru takes issue with Canon's and Nikon's decisions, this is not the place to express that dissatisfaction.
It's perhaps helpful to examine several progressions of ISO speed, as shown in the table below. The columns show, from left to right
To keep the size digestable, I've elided most of the values that don't correspond to integral power-of-2 progressions from ISO 32.
ISO Logarithmic |
ISO Arithmetic |
Canon/ Nikon |
Exact @ ISO 32 |
Exact @ ISO 25 |
---|---|---|---|---|
15° | 25 | — | 25.4 | 25 |
16° | 32 | — | 32 | 31 |
19° | 64 | — | 64 | 63 |
21° | 100 | — | 102 | 100 |
22° | 125 | — | 128 | 126 |
25° | 250 | — | 256 | 252 |
28° | 500 | — | 512 | 504 |
31° | 1000 | — | 1024 | 1008 |
34° | 2000 | — | 2048 | 2016 |
37° | 4000 | — | 4096 | 4032 |
39° | 6400 | — | 6502 | 6400 |
42° | (12,500) | 12,800 | 13,004 | 12,800 |
45° | (25,000) | 25,600 | 26,008 | 25,600 |
48° | (50,000) | 51,200 | 52,016 | 51,200 |
51° | (100,000) | 102,400 | 104,032 | 102,400 |
The progression with exact speeds for integral powers of 2 is arguably the most logical, but the progression with exact speed at ISO 100 is a better match to the current integral power-of-2 ISO values, and is an exact match to the values chosen by Canon and Nikon. Without support from a reliable source, however, we'd simply be guessing at which values are exact. In practice, I don't think it matters all that much, because the actual values are rounded to the nominal values, and may not exactly correspond to any progression.
Anyway, see if this works. JeffConrad ( talk) 11:11, 12 January 2010 (UTC)
I've added a {{Disputed-section}} tag, and {{|fact}} tags for specific items. My previous comments should suffice, but in case they do not, I ask ISOguru/75.118.66.209 to provide a source, other than his opinion, for the “proper” values, as well as the “standard ISO progression”. Because the current ISO progression apparently stops at 10,000, any continuation is speculation. We could forever debate whether Canon and Nikon make the “proper” choices, but both have stature to effectively set standards. Neither ISOguru nor most other Wikipedia editors can make the same claim. It's perhaps much like using EV for ISO 100 speed to indicate luminance. Though some editors here disagree with this practice, it's been established for 40 years, and to rail against it is pointless. Standards organizations, and often equipment manufacturers, set standards and practices; Wikipedia editors simply document them.
If it is thought that this article should comment on Canon's and Nikon's possible deviation from an established pattern, it should be discussed here before such comment is arbitrarily added to the article. JeffConrad ( talk) 02:05, 12 January 2010 (UTC)
So, you are basically making the same argument as "The winner of a war can rewrite history." Just because Nikon and Canon have chosen to disregard convention established by Eastman Kodak, Mees and James, the American Standards Association and the subsequent ISO convention does not mean these numbers are correct. Frankly I couldn't care less Canon and Nikons whims upon the subject, since these are only "ISO equivalents." ISO is a film measurement system that has been crudely modified to express digital exposure ratings. ISOGuru ( talk) 00:14, 11 November 2010 (UTC)
No one has commented on this edit, so I assume the dispute is more or less resolved. If there is no objection, I'll remove the tag that I added. I believe ISOguru's concerns have been adequately (and perhaps excessively) addressed. I also think the Note 3 reference in the last column of the table suffices, and that removing the references from the first column would reduce clutter. If no one objects, I will do this. The situation might change if another manufacturer specifies a speed rating using the progression that ISOguru proposes.
JeffConrad (
talk)
02:39, 15 January 2010 (UTC)
The Canon and Nikon iSO values are NOT exact, because they are taken from doubling OTHER ROUNDED NUMBERS. There is nothing exact about ISO anyway. It represents, in an easy-to-understand manner, changes in negative film density of log [10] 0.30 shifts on negative film. 0.30 has to be a stop on a negative film (3-1/3 stops change per base ten order of magnitude). There is nothing exact about any of the ISO speeds. The only "exact" ISO number, I think it was 100 when the standard for ASA was originally written is a basis for deriving other numbers. ISO values are no different than F/stops, which not only do not always take into account the actual size of the stop, but also do not account for light loss due to internal element refraction and due to zooms and other conditions. ISO film speeds similarly do not give actual film speeds. Manufacturers have routinely called ISO 200 films "100," ISO 640 films as "1600" films, and 4- to 500 films as "800" films. ISO film speeds do not in any way represent actual numerical relationships between film speeds, they are rough denominations that relate to sensitometry-ignorant photographers 0.30 progressions (negative film log 10 density) under or over 100 ISO speed. ISOGuru ( talk) 05:08, 16 November 2010 (UTC)
I removed the note
which was appended to one of the references. Ostensibly, this seems reasonable, but as previously discussed, we don't have an authoritative source for exact values, so the statement is a bit speculative. Because ISO logarithmic speeds are rounded to the nearest integer anyway, the point would seem moot (in the American sense). If it's felt this comment should be included, it should have a source and be a separate note appended to the previous sentence so it's clear to what it applies. JeffConrad ( talk) 21:14, 11 May 2010 (UTC)
The argumentation above bases on two things:
The first is clearly correct. The second is demonstrably incorrect. Look at the ISO rating: there are linear and logarithmic values, though for some reason few people use the latter. But they also make it very clear that the steps are related to powers of 10, not powers of 2. The steps are the tenth root of 10. 10,000 ISO linear is 41° logarithmic. 51° logarithmic is 10 times 41° logarithmic, 100,000, and not 102,400. This makes the table inaccurate. It also means that the current section 1.2 is wrong: doubling the sensitivity adds approximately 3° to the logarithmic scale (closer to 3.0103°).
I believe that this correct procedure is to state this information, and that the camera manufacturers haven't adhered to the intention of the scales. Groogle ( talk) 07:25, 23 February 2010 (UTC)
Thanks for your take, Groogle. While "Photographers" work in powers of 2 with stops, lab technicians, and those practicing the science of densitometry (where ISO/ASA/DIN is determined) work with log sub 10 powers. A D-max of 4.0 above base fog means that a film only lets through 1/10,000 the amount of light that the D-min would admit on a piece of transparent film.
I find it funny that those who criticized, censored, and deleted the correct progressions back in January expected me to easily find a source on a website backing up my claims. I have since misplaced my Petersen's Photographic Library, 1978 Ed. "Increasing Film Speed," which clearly indicates EIs of 10,000. I have a scan from that book for anyone who doesn't believe me, but not hte article. However, with quite a bit of searching, I have found two references to film speed that do include the proper progressions:
"[With reference to the new Kodak TMZ 3200 5056 film:] Can be exposed at speeds of EI 800 and EI 1600 with excellent results. Allows a high degree of enlargement. ... T-MAX P3200 Professional Film Multi-speed panchromatic negative film that combines high to ultra-high (EI 3200 to EI 25000 ) ... "Kodak scientific imaging products" Eastman Kodak Company. Photographic Products Group - 1989 Ed.
"2475 Recording Estar +DK50 [Using this B&Wphotographic developing agent]. Probably the fastest combination in the world. 2475 Recording Estar was designed for low-light surveillance work by bodies such as the FBI. It is a very grainy emulsion only suitable for special effects or for use when no other stock will produce the required results. The basic film speed is 1600 ASA and it can be pushed up to 10,000 ASA, although at this speed [. . .] " From a Kodak leaflet on 2475 Recording film, undated.
So, if someone wants to correct the article, fine. I am done "ranting" on here. But I am not full of_ _ it just because the "infinite" knowledge of the internet only contains incorrect speeds propagated by camera manufacturers who wish all photographic sciences were dead so they could sell more software and printers, and other uneducated photographers who make the same ignorant rounding mistakes.
Another hint for my esteemed colleagues: If log 2 powers were being used here in ASA film speeds, why are they calculated in THIRDS of a stop? Seems rather unusual to me. ISOGuru ( talk) 00:15, 11 November 2010 (UTC)
I just posted not one, but two reliable sources. I don't know what more I need to provide. YOu deleted all of my hard work in January, expecting me to know all of the inner workings and procedures of finding your posts here. Now it appears you don't accept the sources I've provided because they don't have a URL or a digital camera maker's name attached to them. There are plenty of weak points in this article that are not adequately backed up by solid citation, yet you delete mine because it is not formatted correctly, or is a rant? Do you think I made these sources I have posted now up? Who cares what is in the ISO standards. They have a very clear progression. You make arguments similar to "Almost everyone in the world media announced that 2000 was the start of the new millenium, not 2001, so this lends organizational credibility to this argument." ISOGuru ( talk) 22:30, 12 November 2010 (UTC)
Here are some more sources:
"KODAK T-MAX P3200 EI 800-6400 Grain: RMS 18 RP: 125/40 lpm ID: TMZ, 5054 T-Max P3200 has excellent speed characteristics—it can be pushed to EI 50,000 for surveillance work and exposed at EI 3200-6400 for general shooting—with good grain and sharpness at the lower film speeds. We've used T-Max P3200 for many subjects in all kinds of lighting and have found it to be an excellent choice whenever film speeds above EI 800 are required." Source: http://www.photographic.com/film/37/index7.html Retrieved today.
"Delta 3200 Type: Black and White Speed: ISO 1000/DIN 31 Available formats: 35 mm, 120 Granularity: Latitude: EI 1600/33 to EI 6400/39, up to EI 25000/45 with push processing Resolving power: History: Available since 1998 as a competitor to Kodak's T-Max 3200. Unlike Kodak's emulsion, it is available in 120 format. Primary usage: Low light and extreme low light depending on what speed it is exposed and developed at." Source: http://en.wikipedia.org/wiki/List_of_photographic_films NOTE THIS IS RETRIEVED FROM WIKIPEDIA, making it the least reliable source, from what I've experienced here. But it is interesting that this site isn't even consistent with sister articles published by some of the same people.
http://www.apug.org/forums/forum216/34406-ektachrome-e-i-20-000-processing.html Here is a link to formulae that are almost certainly from the exact same EI I mentioned from the 1978 article in "Increasing Film Speed," giving EIs of 10,000 and 20,000. ISOGuru ( talk) 23:16, 12 November 2010 (UTC)
You are doing an op-ed on my credibility in every one of your smarmy posts. EI and ISO are the same exact numbers. So is the first ISO number identical to the numbers used in ASA. There is a document I've posted there that says "25,000 ASA." You keep praising ISO standards (with the 12,500 ISO you don't list), yet you used digital camera speeds as "proper" listing. How is that objective? ISOGuru ( talk) 04:48, 16 November 2010 (UTC)
An examination of some of the ANSI and ISO standards reveals several things:
JeffConrad ( talk) 04:01, 16 November 2010 (UTC)
Ah, but "arcane" is objective. Your argument is totally flawed. 1250 is a rounded ISO/ASA/EI speed. If ISO is going to cave in and introduce ugly numbers, that doesn't seem to prove your point. It just shows that they are willing to cave into pressure from companies that got the numbers wrong.
As for taking Kodak, Fuji, and other film coating companies' use of speeds, I take them over Nikon and Canon, because they were working in some cases at it a CENTURY before Nikon and Canon were.
I still don't understand how it is "speculation" to see the 10 12[.5]* 16 20 25 32 40 50 64 80 *round or drop pattern that is repeated through three iterations in respected, documented literature. ISOGuru ( talk) 04:56, 16 November 2010 (UTC)
At the end of Applying film speed, we state (full disclosure: I think I added this),
citing the notes to Table 2 of ASA PH2.12-1961. As has been discussed here and in Talk for other articles, the APEX proposal was essentially stillborn, so I’m not sure it’s reasonable to still take its recommendations as authoritative. Though I have no reason to suspect that equipment manufacturers ever did otherwise, a fit of the rounded speeds to an exponential function gives a better fit to power-of-ten progression than to a power-of-two progression. The difference is so minor as to be of no practical significance; the difference between actual measured speeds and the rounded values is probably far greater. Nonetheless, the sentence quoted above states as fact what, absent support from a reliable source indicating that this indeed is what manufacturers do, is only a reasonable assumption. Should we keep this statement, revise it, or eliminate it? JeffConrad ( talk) 08:12, 19 December 2010 (UTC)
Most digital cameras have ranges of ISO speeds that match film speeds of 3200 or less; if every digital camera is included in the list, it's going to be an unreadable mess. Is it reasonable to include the PowerShot SX200 IS but not the others? JeffConrad ( talk) 22:23, 16 January 2010 (UTC)
In its current state, the article does not elaborate on the ISO ratings of digital cameras.
I recall from a Consumer Reports study on digital cameras that a high ISO is a good thing for several reasons. One, a high ISO means less light is needed. In other words, a high ISO means one doesn't need to use a flash to get a good photo of a candle-lit birthday cake. It also means that there is less blur when the camera and/or subject is moving because the picture is taken in less time. This is why cameras like the Nikon D3S and the Canon EOS-1D Mark IV, which are professional grade cameras, have been designed to be able to take pictures at 102,400. This article, however, is quite biased against high ISOs. Now, I do know that using a higher ISO can lead it poorer quality (ex: Panasonic DMC-FS15), but this article fails to mention that cameras rated at higher ISOs have less quality degradation at higher ISOs than cameras rated at a lower ISO.
In short, the intro (and the article in general) needs to talk more about the ISO ratings of digital cameras and not focus so much on film because the two are so different that they need separate treatment.-- Humanist Geek ( talk) 08:09, 16 April 2010 (UTC)
"Sensitivity" includes a disambiguation to this page. CMOS and CCD sensors list "sensitivity" in millivolts or volts per lux-second. This isn't touched upon on this page (although it comes close). What does that measurement mean? Don't these sensors "count" charge (electrons) not voltage? Is more volts per lux-second more sensitive or less sensitive? Thanks. —Ben FrantzDale ( talk) 18:58, 15 November 2010 (UTC)
This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 | Archive 2 |
Hi, all,
This is too much to just change in the main entry. May I have some comments so I can fix the proposed text up? My own comments are in [bracketed italics] 2B removed later. (I know there is an !-- Invisible Note to editors -- mechanism, but these comments should be seen on the TalkPage. I'll hassle getting them out later.)
PROPOSED TEXT
Individual silver halide crystals suspended in a film emulsion aggregate into clumps ("grains") of random size. [Grains are not as regular and orderly as the crystals which lie at their heart, and at the heart of the energy storage mechanism that makes it possible to store and later develop a latent image] Even when these are not individually resolved in an image, a texture ("graininess") remains. Higher film speed brings more graininess. [nice direct statement from original more or less] Fine-grain stock, such as film used for portraiture or copying, is "slow", meaning that the amount of light used to expose it must be high or the shutter must be open longer. Fast films, used for shooting in poor light or for shooting fast motion, produce a grainy image. [Easily grasped contrast of different practical situations, also from original, more or less]
Since each grain of silver halide develops in an all-or-nothing way, photographic images actually consist of a mosaic of developed and undeveloped areas. In this sense, film is a threshold detector rather than a linear detector. [This is a delightful insight to present, at a time when so many of us are making the historic transition from "analog" to "digital". However, it didn't have enough of a "compare and contrast" discussion to clarify differences between the two ways of conceptualizing film's function.] If the subject has an edge between light and darkness and that edge falls on a grain, the result will be an area that is all light or all shadow. Fine gradations of grayness are also quantized, so that graininess interferes with the perception of shape from shading as well as with object contours (edges). [As the brain imposes structure on sensation to achieve perception, "shape from shading" has emerged in recent decades as an important mechanism of shape encoding from surfaces, just as contours and their elaboration in the brain is an important mechanism of shape encoding from edges, and of figure/background segmentation. Also, it makes for beautiful b/w photos :-) ] Photographers sometimes exploit film's quantization with high-contrast derivatives ("orthos") that really are only black or white, [These are typically made with photolithography film like Kodalith, hence the name. I put this in to be sure readers understand that it's hard to get even grainy shots to lose their grey-ness, unless special steps are taken. Perhaps it can be dropped to keep everything brief. Opinions? ] but the issue of quantization is moot in most photos, because grains are random in size, overlap, and are not individually resolved in the image. Under such typical circumstances, slow films have higher contrast, and faster films have not only lower contrast, but a much longer gray scale, beloved of available light photographers in journalism and movie making. [There was a problem in the original on this point. Maybe you can say it better, but we need some kind of clarification. An ASA 400 b/w film has what they call a "longer grey scale" than an ASA 25 film. Subjectively, I've always thought the grays of fast film "looked nicer", but technically it means that the negative film goes deeper into highlights before blocking/saturating, and it can throw a few grains into shadows before falling to baseline density at low image intensity.]
Original: "Fast films are also relatively contrasty, for the same reason. That is, an area of the image will consist of bright areas and dark ones with few transitional areas of midtones." This statement is misleading at best. Slow films have a higher gamma.
END proposed text.
Please don't clobber me. If there are better ways to handle a suggested revision, just say. As for the revision itself, entries on technology are of necessity always a work in progress, so this won't be the last change, and not every change has to be made.
Thanks!
Jerry-va
17:09, 27 February 2006 (UTC)
Does anyone know how films speed and the ISO ratings relate to digitalo cameras? I think this would be useful to add.
BEGIN remark Quote: "However, this loss is visible as image noise rather than grain." As someone from the area of digital image processing research I find this a completely non-technical and unsupportable statement. Maybe I am overlooking something. Please define the difference. If analog graininess and digital snow look different because of the square raster, I would understand it. However, from some distance artificial graininess in digital images cannot be discerned from the example given. Note that the figure on the page is also digital, with square pixels.
END remark —Preceding unsigned comment added by 94.212.221.215 ( talk) 22:52, 5 August 2010 (UTC)
A while ago, I removed Delta 3200 from the chart, and today an anonymous user, in what I assume to be a well-meaning edit, added it back (at 3200). The reason that I removed it is that Delta 3200 does not have a true ISO speed of 3200; according to the data sheet, the true ISO speed is 1000. Shooting it at the recommended speed of 3200 is actually " pushing" the film, and will result in higher contrast and less shadow detail than if it were shot at the ISO speed. For this reason, I don't think it's appropriate to list it on the chart. Listing it under 3200 is inaccurate, and listing it under 1000 would be confusing without a lengthy explanation. Similar arguments apply to Kodak's Tmax P3200. -- Coneslayer 18:00, 2005 Apr 17 (UTC)
I have edited the article slightly to remove the common misconception that the f-number is equal to the ratio of the focal length to the aperture diameter. It is not. The f-number is equal to the ratio of the focal length to the diameter of the entrance pupil of the lens. The latter is proportional to the diameter of the aperture. It is true that doubling the f-number halves the diameter of the aperture but it is not true that the aperture diameter is equal to the focal length divided by the f-number.-- Srleffler 04:29, 14 February 2006 (UTC)
The description of ISO film speed method refers only to that for still colour negative film. Wouldn't it be more thorough to mention the ISO 6 method for B&W film; why there is a difference between the methods for B&W and colour film; why chromogenic B&W film doesn't quite fit with either; and the existence of a separate standard for colour reversal film? It might also be worth mentioning that there is no ISO for motion picture colour negative film. I would be happy to write the aditional material, as I have all the relevant standards.
-- Helen Bach 15:50, 31 March 2007 (UTC)
Helen, I realize you wrote this 3-1/2 years ago, but I can't imagine why ECN-2 (and equivalent) motion picture films wouldn't have an identical standard to C-41 (and equivalent). My can of 5201 (Kodak Vision 2 50D) does only have EI ratings, but I would assume that is only because that Kodak assumes that Cinematographers will run tests on their filmstocks. This is similar to the practice of B&W photographers coming up with their own EIs for their favorite stocks, such as an EI of 320 for Kodak Tri-X 5063, or Portra 400NC. ISOGuru ( talk) —Preceding undated comment added 00:45, 11 November 2010 (UTC).
Images of a flower taken at ISO 100 and ISO 1600 on a Canon 400D digital camera. Both images were shot under similar lighting conditions, varying only the ISO setting and shutter speed.
I can understand how they were shot under similar lighting conditions, but the illustration is incredibly fallacious, as the ISO 1600 shot would be overexposed compared to ISO 100. Shutter speed would need to be 16 times faster to achieve the same exposure, ie. 1/5600. This is a 2/3 stop of a difference, and that's assuming that the 1/4000th setting (fastest on that camera) is exposing correctly. Tests (in magazines) show that even shutters in professional cameras overexpose by as much as a whole stop at their highest speed, the problem is even more pronounced in amateur cameras (such as 400D). This test would be a good candidate to be repeated (possibly with the same camera), at shutter speeds of 1/100th and 1/1600th or slower. —The preceding unsigned comment was added by 217.153.194.14 ( talk) 21:01, August 23, 2007 (UTC)
I have a Sony HVR-A1J HDV camcorder with a 1/3" CMOS sensor which can be used as a still camera with images saved to a memory stick. The sensitivity of the camera is defined as: 7 lux at +18db with a normal shutter. Let's take this apart: 7 lux is a little less than one foot candle - sounds great, but that 18db is telling us that the noise level is going to be horrendous. Normal shutter probably refers to something between 1/30 and 1/48 second (25 or 30 frames/sec - this camera doesn't actually scan fields). If we move the gain back down to 0 db, sensitivity is more likely to be in the 400 to 1000 lux range. (Well you can do the math to get an exact number. I'm not going to bother.) This actually puts the camera in a fairly standard professional video camera sensitivity range - ISO 160 (or using our old friend Ektachrome 160 in the Bolex), where you can push the film in processing or turn up the gain as needed.
What would be muchly appreciated is a Wikipedia entry that incorporates a cross reference table comparing all these different units of sensitivity to each other. Competitive manufacturers product literature rarely uses the same standards so very little makes sense - like mixing RMS and EIA watts! -- Mccainre ( talk) 07:32, 7 January 2008 (UTC)
Lux (meter candles) is also used to define ISO speed. And, since there are 10.76 candles at a meter (therefore 10.76 meter candles) (lux) as a candle at one foot ( 1 foot candle), that's only 2/3 of a footcandle.
According to a thread I read on Photo.net, the clearest explanation of ISO by the way, I've read thusfar, defines ASA/ISO as "0.8/the speed point in meter candle seconds. The speed poin is many times. 0.1 density units over gross fog. [base fog?]" and, as an example: "An ASA/ISO 800 film requires an exposure of 0.8/800 = 1/1000 of a meter candle second[. . .]" This is WITHOUT A LENS. So you'd have to compensate for light loss based on T-- (not F/-) stops. ISO and foot- or meter- candles are related. ISOGuru ( talk) 00:56, 11 November 2010 (UTC)
According to light meter, the ISO film speed S is given by S=Kn^2/Lt, where L is the luminance of a medium-brightness area (candela/m^2), n the aperture number, K a constant (usually between 12 and 14), and t is the shutter speed. Usually, medium brightness is taken to be an 18% reflective card. However, this doesn't say anything about the headroom. Should a sensor with a given ISO number be at exactly 18% of saturation for a given luminance L? Or is there a standard amount of headroom? I've searched a bit and I found numbers of 106%, 170%, and 141% for the saturation level. What does the ISO document say about it? This information is missing. See e.g. [1], [2], [3]. Han-Kwang ( t) 15:21, 10 October 2007 (UTC)
(copied from Talk:Light meter) I see, so the equation n^2/t = LS/K is a simply a definition of what the reading that a light meter should produce for a given luminance, even though K is somewhat variable. But as a photographer, of course I would want to know how much headroom I will get if I point the light meter at a 18% card. As you say, officially the saturation level should be 141% (1/2 stop above 100%), but in practice YMMV (e.g. my digital compact camera seems to aim for 18/100 rather than 18/141). Maybe this subject really belongs on film speed, where I also asked this question. Anyway, I think the focal plane exposure is given by H=pi L t/4 n^2 (for objects far away from the lens), so Ssat = 78/Hs = 312 n^2/ (pi*Lsat*t) where Lsat is the luminosity that just saturates the sensor. I guess that 78 comes from 100*pi/4, so Ssat=100 n^2/(Lsat*t), which seems to be an elegant equation -- would it be appropriate to mention on film speed? Han-Kwang ( t) 23:43, 10 October 2007 (UTC)
(copied from
Talk:Light meter) I've posted something on
Talk: film speed. Now that I have read Dicklyon's posts here I see that my post there is a re-write of the end of his previous post - ie that the 78 factor in the Ssat formula comes from 141/18. The formula for focal plane exposure used in 12232 (Eq 2) takes flare exposure (Hf), cos^4 loss, lens transmission factor (T) and vignettng factor (v) into account. The pi/4 combines with the other losses (T v cos^4theta, with Hf << H) to produce 65/100 (which is 0.83 pi / 4), so the formula for arithmetic mean focal plane exposure is 65 La t / (100 A^2) where La is the arithmetic mean scene luminance and A is your N. On axis the focal plane exposure would be 0.88 pi L t / (4 A^2).
Helen Bach
22:47, 11 October 2007 (UTC)
(unindent) To Helen: 1) OK for the vignetting, but after some thinking I don't see why it is cos^4 rather than cos^2. One cos(theta) comes from the angle of incidence onto the lens, and the other cos(theta) from the angle of incidence onto the focal plane. Derivation:
D ,-| b o |,-' --------------------+----- ,-' | f ,-' o/cos(theta),-' ,-' spatial angle dOmega ,-' |,-' a |
a is a small surface with a luminance L; the surface has an intensity I=L a cos(theta) [candela] and sees the lens (at a distance o>>f) with a spatial angle dΩ=D^4 cos(theta) pi/4 o^2 . The flux as captured by the lens is
The image in the focal plane has a surface b=af^2/o^2. The illuminance E at the focal plane is then
With D=f/N,
Of course, you can add extra factors for vignetting v(theta) and a lens transmission T,but that doesn't explain the cos^4.
2) and 3) - OK, that's the difference between gamma 2.2 and sRGB, but that's not going to be a big effect at 1 stop below JPG saturation.
4) It looks like (consumer) camera manufacturers are ignoring that part of the ISO standard.
To Dick: aha, 118/256 is 18.4% of saturation in gamma=2.2 and 18.0% in sRGB. (Are you sure it wasn't 18/255 by the way?) And then we are actually back to where I started: SOS rating S (100, 200, 400, 800, etc.) is equivalent to a ISO saturation speed, except that the SOS number refers to saturation of the output JPG image and the ISO number refers to saturation of the sensor.
If one of you can explain the cos^4 factor to me, I think it's time to expand the article.
Han-Kwang ( t) 07:16, 13 October 2007 (UTC)
How time flies. I'm still working on the draft I promised. Meanwhile, how about changing the arithmetic - logarithmic conversion formulae to the one implicit in the speed definitions given in ISO 6 and ISO 5800, and stated explicitly in ISO 2240; and the derived inverse?
This is the conversion method derived from the two speed definitions in each of ISO 6 and ISO 5800, and stated explicitly in ISO 2240: S° = 1+10 log S
This is the inverse of the above, which is not specifically mentioned in the Standards: S = 10^(S°/10) / 1.26
All base 10 logs.
Helen Bach 16:36, 10 October 2007 (UTC) —Preceding unsigned comment added by Helen Bach ( talk • contribs) 16:33, 10 October 2007 (UTC)
It is stated explicitly in ISO 2240, and can be arrived at by simple substitution in the speed formulae given in ISO 6 and ISO 5800. Its ancestry goes back further than that, but those are the three current standards. The relationship is based on the definitions of arithmetic and logarithmic speeds, not on a purely mathematical correlation between the integer pairs 100/21, 200/24 etc. Helen Bach 03:59, 11 October 2007 (UTC)
Will the formulae be changed? What happens next? I'm new to all this. By the way, which table in 12232 are you referring to? Thanks.
Helen Bach
22:11, 11 October 2007 (UTC)
I removed this:
Reasons:
Han-Kwang ( t) 00:19, 7 January 2008 (UTC)
I think the article would benefit from a photo comparison of different ISO settings. I like Dicklyon's suggestion to have a picture with something that moves against a steady background. It would be nice, though, if the picture had some aesthetic value as well when cropped (not scaled) to 250x150 px. Han-Kwang ( t) 09:40, 8 January 2008 (UTC)
Where does the information that the original Kodachrome was ASA 6 come from? I've read in some sources that it was 8 and in some that it was 10, but never 6. —Preceding unsigned comment added by 130.232.17.50 ( talk) 09:23, 6 May 2008 (UTC)
Since ASA was in flux before the 1950s, a speed of "6" in WWII does not necessarily correspond to a speed of "6" ASA today. While this wasn't the case with reversal, to be sure, ASA speeds for B&W were effectively doubled in the 1950s. I have no source to back this up, but I've seen it mentioned many many times by those knowledgeable in such things in Photography Fora on the internet. —Preceding unsigned comment added by ISOGuru ( talk • contribs) 23:52, 10 November 2010 (UTC)
Parts of the article seem to be written more to convince the reader that the author knows the subject than to explain the subject to the reader.
Could it be simplified - perhaps by adding more explanations and links? Perhaps by adding very short summaries to each section?
One thing I had problems with was "clipped or bloomed". To me they are not well defined terms. If it is standard terminology, it would be good to explain them, either here or in separate articles. Mlewan ( talk) 07:12, 31 May 2008 (UTC)
I'm an amateur who understands film sensitivity and was looking for an explanation about digital sensitivity. I do not pretend to understand the math or the formulae for either film or digital. From my perspective, what is missing in this article is a layperson's summary of what generates digital noise. The key is on "layperson". That will probably lead to a major simplification and result in long and endless debates about how much simplification is appropriate! I don't know the answer to that. but I do know that this article as it exists today (3 Feb 2009) is way over my head and provides me with no useful information.
Also, the eraser images above. For me, the blurring confuses the demonstration of noise. I do understand why the image is blurred. Showing two effects in one photo will lead to confusion among those who come here seeking info. Three shots would be a better demo. But make the slow shot at a reasonable speed that people would use for hand held. I believe that few point and shoot cameras would let one take a shot at 1/5th without some warning, and most users of DSLR would probably understand that 1/5th is too slow for hand held - even with vibration reduction. (Though I'd probably still push it and hope!) [[[Special:Contributions/207.236.137.2|207.236.137.2]] ( talk) 18:47, 3 February 2009 (UTC)Peter in Canada]
I am struggling with the relationship between "exposure index" and film "sensitivity". The exposure index section confuses me:
That description and the lengthy example that follows it seem more concerned with "arbitrary exposure compensation" than "film speed" calibration. I've got it into my head that:
Where am I going wrong? -- Redbobblehat ( talk) 22:43, 16 February 2009 (UTC)
As it stood prior to the 8 January 2010 edit by 75.118.66.209, the table agreed with ISO 12232:1998 for speeds up to 10,000; absent a persuasive argument to the contrary, I think we need to treat that standard as authoritative. Both ISO 12232:1998 and CIPA DC-004 2004 stop at 10,000. I don't have ISO 12232:2006, but if it gives speeds beyond 10,000, those values should be used; if not, we should defer to values given by camera manufacturers. ASA PH2.12-1961 (Table 2, which compared arithmetic and logarithmic parameters) showed a value of 12,500, and this table was included in Appendix 2 of ANSI PH3.49-1971; the table was not included in ISO 2720:1974. Because that value hasn't been repeated in almost 40 years, it's difficult to see it as controlling.
More often than not, standardization lags practice, and accordingly, standards often simply document practice. Canon and Nikon have stated the higher ISO speeds as they have, and absent solid authority to the contrary, those are the de facto values. The role of Wikipedia is to document, not advocate, and we simply can't arbitrarily replace a widely accepted value with one of our own, no matter how logical a particular editor may think it.
I agree with 75.118.66.209 that the ISO rounding is somewhat arbitrary, but it follows long-established practice, and in any event, ‘tis as ‘tis. Whether the rounding is “improper” is a matter of personal opinion. In theory, speeds progress in steps of the cube root of 2, and I suspect (but cannot document) that meter calibrations make that assumption; the notes to Table 2 of ASA PH2.12-1961 stated as much. But the notes to that table stated that the “exact” value of ASA 25 was 26.7 due to the arcane conversion between ASA logarithmic and arithmetic speeds. If that is still the case, insisting on “proper” values for every speed would lead to quite different from those to which we are accustomed. Because APEX never really caught on, I'm not sure that table is still meaningful; more recent standards (e.g., ISO 2720-1974) make no mention of it.
Absent an authoritative source, I'm not sure it's possible to determine the “exact” values for each speed. If indeed it were possible, insisting on “exact” values would require changing almost every value in the table. Given that speeds are rounded to the nearest 1/3 of an exposure step anyway, the quest for exact values seems pointless.
Accordingly, I've restored the ISO speeds to their previous values. If 75.118.66.209 can provide an authoritative source for the values he suggested, the matter is of course open to discussion; otherwise, I think he should refrain from further such edits before discussing the matter here. JeffConrad ( talk) 02:20, 11 January 2010 (UTC)
Despite repeated requests for sources, 75.118.66.209 insists on adding unsourced material that in some cases is essentially
original research (e.g., “higher speeds can be extrapolated”) and in other cases is unsupported personal opinion (e.g., “corrupted”). When material is challenged, the
burden of evidence is on the editor adding the material, and this editor defiantly refuses to provide any supporting material or even respond on the talk page. Accordingly, I've removed the unsourced material, in accordance with
WP:V.
JeffConrad (
talk)
20:44, 11 January 2010 (UTC)
I think most of us can work out progressions of speeds, but we cannot displace de facto standard values with our personal preferences. In any event, material like “If they called the values "100,000,000 and 500,000,000" that would make the numbers right too :-/ Learn some basic math. . .” is clearly inappropriate for an article, and it's difficult to see this as a good-faith edit. And the comment “Its on” seems an obvious challenge to an edit war. Accordingly, I suggest we treat this as vandalism, and I have so warned ISOguru. Anyone else?
JeffConrad (
talk)
As the article stands, it includes unsupported personal opinion that's at odds with de facto standard values. I think we should follow WP policy and insist that controversial matherial be supported, but I am not going to waste time in an edit war with ISOguru/75.118.66.209, who apparently sees no need for sources or discussion.
JeffConrad (
talk)
23:48, 11 January 2010 (UTC)
I've made some changes in attempt to satisfy ISOguru while keeping to what can be supported by reliable sources. ISO 12232:1998 does not specify a speed greater than 10,000, but the upper limit for Snoise 10,000 is given as 12,500, suggesting that ISO may have envisioned the progression that ISOguru claims. But this is speculation, and at present, the only devices with speeds greater than 10,000 have specified speeds using a power-of-2 progression that continues from the highest previously realized speed of 6400. Because these speeds are not given by ISO, they are ISO equivalent speeds, as the comment in the table already notes. Because values using the Canon/Nikon progression have actually been specified, I've restored those values to the table rather than speculate on what ISO intended or may eventually adopt. If another manufacturer announces a product with a speed using the progression that ISOguru proposes, I suggest we address it at that time by changing the entry to something like
I've tried to address ISOguru's issue in Note 3. Although there is some speculation, I've made it clear that such is the case. Without some speculation, the alternative progression cannot be addressed until we have a reliable source. Hopefully, this will be acceptable to all concerned.
I've removed references to “proper” value and “corrupted”, because these terms are non-NPOV, and accordingly have no place in a Wikipedia article. If ISOguru takes issue with Canon's and Nikon's decisions, this is not the place to express that dissatisfaction.
It's perhaps helpful to examine several progressions of ISO speed, as shown in the table below. The columns show, from left to right
To keep the size digestable, I've elided most of the values that don't correspond to integral power-of-2 progressions from ISO 32.
ISO Logarithmic |
ISO Arithmetic |
Canon/ Nikon |
Exact @ ISO 32 |
Exact @ ISO 25 |
---|---|---|---|---|
15° | 25 | — | 25.4 | 25 |
16° | 32 | — | 32 | 31 |
19° | 64 | — | 64 | 63 |
21° | 100 | — | 102 | 100 |
22° | 125 | — | 128 | 126 |
25° | 250 | — | 256 | 252 |
28° | 500 | — | 512 | 504 |
31° | 1000 | — | 1024 | 1008 |
34° | 2000 | — | 2048 | 2016 |
37° | 4000 | — | 4096 | 4032 |
39° | 6400 | — | 6502 | 6400 |
42° | (12,500) | 12,800 | 13,004 | 12,800 |
45° | (25,000) | 25,600 | 26,008 | 25,600 |
48° | (50,000) | 51,200 | 52,016 | 51,200 |
51° | (100,000) | 102,400 | 104,032 | 102,400 |
The progression with exact speeds for integral powers of 2 is arguably the most logical, but the progression with exact speed at ISO 100 is a better match to the current integral power-of-2 ISO values, and is an exact match to the values chosen by Canon and Nikon. Without support from a reliable source, however, we'd simply be guessing at which values are exact. In practice, I don't think it matters all that much, because the actual values are rounded to the nominal values, and may not exactly correspond to any progression.
Anyway, see if this works. JeffConrad ( talk) 11:11, 12 January 2010 (UTC)
I've added a {{Disputed-section}} tag, and {{|fact}} tags for specific items. My previous comments should suffice, but in case they do not, I ask ISOguru/75.118.66.209 to provide a source, other than his opinion, for the “proper” values, as well as the “standard ISO progression”. Because the current ISO progression apparently stops at 10,000, any continuation is speculation. We could forever debate whether Canon and Nikon make the “proper” choices, but both have stature to effectively set standards. Neither ISOguru nor most other Wikipedia editors can make the same claim. It's perhaps much like using EV for ISO 100 speed to indicate luminance. Though some editors here disagree with this practice, it's been established for 40 years, and to rail against it is pointless. Standards organizations, and often equipment manufacturers, set standards and practices; Wikipedia editors simply document them.
If it is thought that this article should comment on Canon's and Nikon's possible deviation from an established pattern, it should be discussed here before such comment is arbitrarily added to the article. JeffConrad ( talk) 02:05, 12 January 2010 (UTC)
So, you are basically making the same argument as "The winner of a war can rewrite history." Just because Nikon and Canon have chosen to disregard convention established by Eastman Kodak, Mees and James, the American Standards Association and the subsequent ISO convention does not mean these numbers are correct. Frankly I couldn't care less Canon and Nikons whims upon the subject, since these are only "ISO equivalents." ISO is a film measurement system that has been crudely modified to express digital exposure ratings. ISOGuru ( talk) 00:14, 11 November 2010 (UTC)
No one has commented on this edit, so I assume the dispute is more or less resolved. If there is no objection, I'll remove the tag that I added. I believe ISOguru's concerns have been adequately (and perhaps excessively) addressed. I also think the Note 3 reference in the last column of the table suffices, and that removing the references from the first column would reduce clutter. If no one objects, I will do this. The situation might change if another manufacturer specifies a speed rating using the progression that ISOguru proposes.
JeffConrad (
talk)
02:39, 15 January 2010 (UTC)
The Canon and Nikon iSO values are NOT exact, because they are taken from doubling OTHER ROUNDED NUMBERS. There is nothing exact about ISO anyway. It represents, in an easy-to-understand manner, changes in negative film density of log [10] 0.30 shifts on negative film. 0.30 has to be a stop on a negative film (3-1/3 stops change per base ten order of magnitude). There is nothing exact about any of the ISO speeds. The only "exact" ISO number, I think it was 100 when the standard for ASA was originally written is a basis for deriving other numbers. ISO values are no different than F/stops, which not only do not always take into account the actual size of the stop, but also do not account for light loss due to internal element refraction and due to zooms and other conditions. ISO film speeds similarly do not give actual film speeds. Manufacturers have routinely called ISO 200 films "100," ISO 640 films as "1600" films, and 4- to 500 films as "800" films. ISO film speeds do not in any way represent actual numerical relationships between film speeds, they are rough denominations that relate to sensitometry-ignorant photographers 0.30 progressions (negative film log 10 density) under or over 100 ISO speed. ISOGuru ( talk) 05:08, 16 November 2010 (UTC)
I removed the note
which was appended to one of the references. Ostensibly, this seems reasonable, but as previously discussed, we don't have an authoritative source for exact values, so the statement is a bit speculative. Because ISO logarithmic speeds are rounded to the nearest integer anyway, the point would seem moot (in the American sense). If it's felt this comment should be included, it should have a source and be a separate note appended to the previous sentence so it's clear to what it applies. JeffConrad ( talk) 21:14, 11 May 2010 (UTC)
The argumentation above bases on two things:
The first is clearly correct. The second is demonstrably incorrect. Look at the ISO rating: there are linear and logarithmic values, though for some reason few people use the latter. But they also make it very clear that the steps are related to powers of 10, not powers of 2. The steps are the tenth root of 10. 10,000 ISO linear is 41° logarithmic. 51° logarithmic is 10 times 41° logarithmic, 100,000, and not 102,400. This makes the table inaccurate. It also means that the current section 1.2 is wrong: doubling the sensitivity adds approximately 3° to the logarithmic scale (closer to 3.0103°).
I believe that this correct procedure is to state this information, and that the camera manufacturers haven't adhered to the intention of the scales. Groogle ( talk) 07:25, 23 February 2010 (UTC)
Thanks for your take, Groogle. While "Photographers" work in powers of 2 with stops, lab technicians, and those practicing the science of densitometry (where ISO/ASA/DIN is determined) work with log sub 10 powers. A D-max of 4.0 above base fog means that a film only lets through 1/10,000 the amount of light that the D-min would admit on a piece of transparent film.
I find it funny that those who criticized, censored, and deleted the correct progressions back in January expected me to easily find a source on a website backing up my claims. I have since misplaced my Petersen's Photographic Library, 1978 Ed. "Increasing Film Speed," which clearly indicates EIs of 10,000. I have a scan from that book for anyone who doesn't believe me, but not hte article. However, with quite a bit of searching, I have found two references to film speed that do include the proper progressions:
"[With reference to the new Kodak TMZ 3200 5056 film:] Can be exposed at speeds of EI 800 and EI 1600 with excellent results. Allows a high degree of enlargement. ... T-MAX P3200 Professional Film Multi-speed panchromatic negative film that combines high to ultra-high (EI 3200 to EI 25000 ) ... "Kodak scientific imaging products" Eastman Kodak Company. Photographic Products Group - 1989 Ed.
"2475 Recording Estar +DK50 [Using this B&Wphotographic developing agent]. Probably the fastest combination in the world. 2475 Recording Estar was designed for low-light surveillance work by bodies such as the FBI. It is a very grainy emulsion only suitable for special effects or for use when no other stock will produce the required results. The basic film speed is 1600 ASA and it can be pushed up to 10,000 ASA, although at this speed [. . .] " From a Kodak leaflet on 2475 Recording film, undated.
So, if someone wants to correct the article, fine. I am done "ranting" on here. But I am not full of_ _ it just because the "infinite" knowledge of the internet only contains incorrect speeds propagated by camera manufacturers who wish all photographic sciences were dead so they could sell more software and printers, and other uneducated photographers who make the same ignorant rounding mistakes.
Another hint for my esteemed colleagues: If log 2 powers were being used here in ASA film speeds, why are they calculated in THIRDS of a stop? Seems rather unusual to me. ISOGuru ( talk) 00:15, 11 November 2010 (UTC)
I just posted not one, but two reliable sources. I don't know what more I need to provide. YOu deleted all of my hard work in January, expecting me to know all of the inner workings and procedures of finding your posts here. Now it appears you don't accept the sources I've provided because they don't have a URL or a digital camera maker's name attached to them. There are plenty of weak points in this article that are not adequately backed up by solid citation, yet you delete mine because it is not formatted correctly, or is a rant? Do you think I made these sources I have posted now up? Who cares what is in the ISO standards. They have a very clear progression. You make arguments similar to "Almost everyone in the world media announced that 2000 was the start of the new millenium, not 2001, so this lends organizational credibility to this argument." ISOGuru ( talk) 22:30, 12 November 2010 (UTC)
Here are some more sources:
"KODAK T-MAX P3200 EI 800-6400 Grain: RMS 18 RP: 125/40 lpm ID: TMZ, 5054 T-Max P3200 has excellent speed characteristics—it can be pushed to EI 50,000 for surveillance work and exposed at EI 3200-6400 for general shooting—with good grain and sharpness at the lower film speeds. We've used T-Max P3200 for many subjects in all kinds of lighting and have found it to be an excellent choice whenever film speeds above EI 800 are required." Source: http://www.photographic.com/film/37/index7.html Retrieved today.
"Delta 3200 Type: Black and White Speed: ISO 1000/DIN 31 Available formats: 35 mm, 120 Granularity: Latitude: EI 1600/33 to EI 6400/39, up to EI 25000/45 with push processing Resolving power: History: Available since 1998 as a competitor to Kodak's T-Max 3200. Unlike Kodak's emulsion, it is available in 120 format. Primary usage: Low light and extreme low light depending on what speed it is exposed and developed at." Source: http://en.wikipedia.org/wiki/List_of_photographic_films NOTE THIS IS RETRIEVED FROM WIKIPEDIA, making it the least reliable source, from what I've experienced here. But it is interesting that this site isn't even consistent with sister articles published by some of the same people.
http://www.apug.org/forums/forum216/34406-ektachrome-e-i-20-000-processing.html Here is a link to formulae that are almost certainly from the exact same EI I mentioned from the 1978 article in "Increasing Film Speed," giving EIs of 10,000 and 20,000. ISOGuru ( talk) 23:16, 12 November 2010 (UTC)
You are doing an op-ed on my credibility in every one of your smarmy posts. EI and ISO are the same exact numbers. So is the first ISO number identical to the numbers used in ASA. There is a document I've posted there that says "25,000 ASA." You keep praising ISO standards (with the 12,500 ISO you don't list), yet you used digital camera speeds as "proper" listing. How is that objective? ISOGuru ( talk) 04:48, 16 November 2010 (UTC)
An examination of some of the ANSI and ISO standards reveals several things:
JeffConrad ( talk) 04:01, 16 November 2010 (UTC)
Ah, but "arcane" is objective. Your argument is totally flawed. 1250 is a rounded ISO/ASA/EI speed. If ISO is going to cave in and introduce ugly numbers, that doesn't seem to prove your point. It just shows that they are willing to cave into pressure from companies that got the numbers wrong.
As for taking Kodak, Fuji, and other film coating companies' use of speeds, I take them over Nikon and Canon, because they were working in some cases at it a CENTURY before Nikon and Canon were.
I still don't understand how it is "speculation" to see the 10 12[.5]* 16 20 25 32 40 50 64 80 *round or drop pattern that is repeated through three iterations in respected, documented literature. ISOGuru ( talk) 04:56, 16 November 2010 (UTC)
At the end of Applying film speed, we state (full disclosure: I think I added this),
citing the notes to Table 2 of ASA PH2.12-1961. As has been discussed here and in Talk for other articles, the APEX proposal was essentially stillborn, so I’m not sure it’s reasonable to still take its recommendations as authoritative. Though I have no reason to suspect that equipment manufacturers ever did otherwise, a fit of the rounded speeds to an exponential function gives a better fit to power-of-ten progression than to a power-of-two progression. The difference is so minor as to be of no practical significance; the difference between actual measured speeds and the rounded values is probably far greater. Nonetheless, the sentence quoted above states as fact what, absent support from a reliable source indicating that this indeed is what manufacturers do, is only a reasonable assumption. Should we keep this statement, revise it, or eliminate it? JeffConrad ( talk) 08:12, 19 December 2010 (UTC)
Most digital cameras have ranges of ISO speeds that match film speeds of 3200 or less; if every digital camera is included in the list, it's going to be an unreadable mess. Is it reasonable to include the PowerShot SX200 IS but not the others? JeffConrad ( talk) 22:23, 16 January 2010 (UTC)
In its current state, the article does not elaborate on the ISO ratings of digital cameras.
I recall from a Consumer Reports study on digital cameras that a high ISO is a good thing for several reasons. One, a high ISO means less light is needed. In other words, a high ISO means one doesn't need to use a flash to get a good photo of a candle-lit birthday cake. It also means that there is less blur when the camera and/or subject is moving because the picture is taken in less time. This is why cameras like the Nikon D3S and the Canon EOS-1D Mark IV, which are professional grade cameras, have been designed to be able to take pictures at 102,400. This article, however, is quite biased against high ISOs. Now, I do know that using a higher ISO can lead it poorer quality (ex: Panasonic DMC-FS15), but this article fails to mention that cameras rated at higher ISOs have less quality degradation at higher ISOs than cameras rated at a lower ISO.
In short, the intro (and the article in general) needs to talk more about the ISO ratings of digital cameras and not focus so much on film because the two are so different that they need separate treatment.-- Humanist Geek ( talk) 08:09, 16 April 2010 (UTC)
"Sensitivity" includes a disambiguation to this page. CMOS and CCD sensors list "sensitivity" in millivolts or volts per lux-second. This isn't touched upon on this page (although it comes close). What does that measurement mean? Don't these sensors "count" charge (electrons) not voltage? Is more volts per lux-second more sensitive or less sensitive? Thanks. —Ben FrantzDale ( talk) 18:58, 15 November 2010 (UTC)