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![]() | A fact from Perspective control lens appeared on Wikipedia's
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The diagram is nice, but having actual images for both tilt, shift, and tilt/shift (vs. uncorrected). Cburnett 02:49, 20 October 2007 (UTC)
It would be good if someone could relate which (if any) digital SLR systems have compatibility with shift lenses, given how few there are. Or if none, simply state that fact. 82.10.108.49 ( talk) 21:53, 26 February 2008 (UTC)
Perhaps I’m being too fussy, but the description of the new Nikkor lenses was reading more like a Nikon brochure than an encyclopedia article. The buzzwords like “electromagnetic diaphragm” and “CMOS” apply equally to Canon, but they’re irrelevant to this article (as probably is “FX-format”, as well), serving only to clutter things up. I also question the statement that only the full-frame formats use the full capabilities of the lenses. It’s true that smaller formats (such as Canon’s 1.6 factor and Nikon’s 1.5 factor) don’t use the full image circles, but they afford some advantages as well (e.g., the shift is a greater fraction of the format size). Arguably, the greatest difference is the narrower ange of view, which sometimes is a problem and other times is an advantage. NPOV would seem to require comparable treatment of Canon and Nikon (and any other) lenses, and throwing in all the buzzwords forces the reader to wade through all sorts of material that has little real bearing on the substance of the article. JeffConrad ( talk) 04:46, 4 July 2008 (UTC)
I suppose there could be some point in mentioning the electromagnetic diaphragm on the PC-E Nikkor lenses if their preset operation on cameras other than the D3, D300, and D700 were contrasted with the mechanical preset operation of the PC Micro-Nikkor f/2.8D (non-E). I’ve added this to the article. If this information seems superfluous, get rid of it. I still recommend eliminating the last sentence in the paragraph; this article is about lenses, not camera bodies. JeffConrad ( talk) 07:41, 4 July 2008 (UTC)
I've moved the discussion of aperture control to a new section to lessen the clutter in describing available lenses. I'm not sure this material ultimately belongs here, although I'm also not sure where it does belong—perhaps in its own article. I'm a bit surprised that there is almost no mention of this in WP, but I suppose that, aside from PC/TS lenses, it's little more than a historical curiosity. JeffConrad ( talk) 04:26, 7 July 2008 (UTC)
The vast majority of lenses/adapters mentioned in this article include tilt functions as well as shift, so the current title is somewhat misleading. Should the page be moved and expanded accordingly? Currently, Tilt-shift lens redirects to Tilt-shift photography, which doesn't make sense (a lens is not a technique). JeffConrad ( talk) 02:18, 8 July 2008 (UTC)
Shouldn’t the term used in the gallery match the article title? Using “perspective correction” one place and “perspective control” in another just confuses the reader. Either term is workable, but the former may be preferable because it is more supplier neutral. JeffConrad ( talk) 21:49, 8 July 2008 (UTC)
This article is about perspective control but this is only half the story for a tilt-shift lens so why is it re-directed here? There needs to be some description of the tilt effect which is mainly to control focus. A tilt-shift article is needed. Unfortunately the tilt-shift photography article has morphed into an article on the photoshop technique. Kwenchin ( talk) 23:21, 28 February 2010 (UTC)
Perhaps once again I'm being too touchy, but this is starting to look more like a personal essay than an encyclopedia article. JeffConrad ( talk) 21:53, 31 July 2008 (UTC)
I was actually starting to think that the lens gallery is getting too large. For the most part, each lens looks pretty much the same. Maybe we could whittle this down to four that show the widest variety between the lenses and put the rest on Commons? howcheng { chat} 02:50, 1 August 2008 (UTC)
Can editor 199.227.143.21 provide a source for the availability of K-mount Zenitar tilt/shift lenses? I see MC Arsat versions of these lenses, on both the Arsenal site and the Hartblei site, but can find nothing on the Zenitar site. Whatever the source, the other available mounts should also be mentioned. JeffConrad ( talk) 07:44, 1 August 2008 (UTC)
There are serious compatibility issues, beyond those stated or implied in the article, with Nikon PC-E lenses and various Nikon camera bodies. Automatic aperture control is only available with the D300, D3, and D700 bodies; some other bodies support the electronic preset aperture control via the lens pushbutton, but apparently some do not. Ken Rockwell describes these problems in considerable detail; I've had only brief contact with a 24 mm PC-E lens, so I can't confirm his findings. On some camera bodies with built-in flash, the lenses cannot be rotated if maximum rise is employed; on others, it may not even be possible to set maximum rise without hitting the bottom of the prism housing.
Canon TS-E lenses provide automatic aperture control with any EF-mount bodies, but clearance of the prism housing is an issue on some DSLRs with built-in flashes.
To my knowledge, neither Canon nor Nikon have bothered to identify these incompatibilities. I'm not sure the responsibility falls to this article, but adding at least a general caveat might be a good idea. I'm lukewarm on including a link to Rockwell's article, because I've found his writings to be uneven in quality and even accuracy. Currently, though, I'm not sure what else is available, so perhaps a footnote mentioning an external link would point the reader to the article without the implication of endorsement. I know of no similar article that examines clearances on Canon DSLRs. JeffConrad ( talk) 21:29, 31 August 2008 (UTC)
yes, you lose resolution in the distant areas because they're recorded on a smaller area of film
I suppose it's possible to look at it this way, but it's mighty unusual statement. And even if one were to do so, this would be true for any lens; what in the world does it have to do with perspective control? And what is “lost depth of field due to the angle of the film/sensor plane to the subject”? Tilting a lens changes the orientation of the plane of focus and changes the shape and orientation of the depth of field, but there is no “lost” depth of field. And again, what does it have to do with perspective control? JeffConrad ( talk) 03:32, 1 September 2008 (UTC)
Perhaps I should have clarified my comment on the first issue: obviously, it's more difficult to resolve details on an object at great distance from the camera than it is to resolve those details on the same object close to the camera. What's unusual is to say that resolution in distant objects is “lost”; the resolution was never there. I cannot imagine anyone thinking that software perspective control would somehow improve resolution in distant objects; unless I've really misunderstood the intent, I cannot see why the statement I deleted belongs in this article. JeffConrad ( talk) 04:01, 1 September 2008 (UTC)
Most of this section really doesn't belong in this article; I originally added it only because there wasn't another good source to explain what an automatic diaphragm was. If there is no objection, I'll move most of this section to the Aperture article, leaving only material that specifically relates to tilt/shift lenses. JeffConrad ( talk) 00:14, 12 December 2008 (UTC)
The paragraph on using shift to negate the effects of motion blur in aerial photography is nearly incomprehensible as well as unsourced. Absent a reliable source, as well as a better explanation, I think this material should be removed. JeffConrad ( talk) 03:47, 4 September 2009 (UTC)
The linked article Tilt-shift miniature faking doesn't really have anything to do with the use of tilt; it's almost as if that article attempts to describe digitally faking a technique that doesn't really fake miniatures. In the second paragraph under Techniques, that article states
That statement is correct for two reasons:
The emphasis of that article is a bit difficult to discern, but it appears to describe a technique (e.g., Smallgantics that actually does simulate DoF that obtains from close-up photography. JeffConrad ( talk) 09:09, 7 September 2009 (UTC)
The section on lenses doesn't strike me as an advert; perhaps the sentence on the 35 mm PC-Nikkor could be slightly rewritten so it sounds less like bragging rights, but otherwise, I'm not sure how this section could be significantly changed and still adequately describe the lenses. IP editor made no comment, so it's impossible to address his objections; perhaps he doesn't understand the significance of things such as automatic diaphragms. In any event, unless the editor can indicate why the section isn't neutral, I recommend we remove the tag. JeffConrad ( talk) 23:02, 25 March 2010 (UTC)
I've updated the section to reflect current status (except for the Leica S 30 mm tilt/shift, for which I have no information). I've put the manufacturers in alphabetical order so that we don't imply that Canon and Nikon rule the world. I've also removed mention of the PC-Nikkor 35 mm; it's no longer available, and it's already mentioned in the lead section. Likewise, the image of the PC-Nikkor 35 mm is already included in the gallery.
JeffConrad (
talk)
02:06, 26 March 2010 (UTC)
I agree that the 1961 PC-Nikkor should be shown—I erred in saying the image in the gallery was of that lens. But the lens should be shown where it's discussed, not in the section on available lenses. And arguably at least as significant is the world's first tilt/shift lens, because all but one of the current available lenses includes tilt. Where do we stop? If we want to include every shift lens ever made, we should re-title the section or create a separate section for discontinued lenses. JeffConrad ( talk) 06:07, 26 March 2010 (UTC)
I agree with sizing the image to match the diagram. Though normal WP policy is “let the user decide”, common sense must prevail. Here, I think aesthetics dictate.
On a side note: the left-hand side of the top of the figure isn't correct—it should show the limit of the angle of view cutting off the top of the building. Any chance of getting this fixed?
Editor
90.195.131.21, who added the {{
advert}} tag, further explained the edit:
To an extent, I think the editor has a point. On the other hand, I think PC and TS lenses are somewhat different beasts, because they incorporate, to varying degree, special features unfamiliar to many photographers. And I also wonder if we ever could agree on which lenses are “notable”; for me, the list might include
A case might be made for including the original Nikon PC Micro-Nikkor 85 mm lens as the first “macro” TS lens, but I think its 0.5 magnification is simply an incremental gain from the Canon TS-E 90 mm lens's 0.29. Of course, others well might disagree.
Perhaps we could say something like “24 mm, 45 mm, and 90 mm PC-E lenses” rather than giving all the details. I'm not sure the maximum aperture is of interest to most readers, but I do think features such as automatic aperture control and independent rotation of shift and tilt are significant and merit mention.
Thoughts? JeffConrad ( talk) 22:35, 26 March 2010 (UTC)
I've cleaned up the lead section a bit, and updated a couple of comments to reflect the improvements in the image circles of recent lenses, and the availability of longer focal lengths that almost certainly aren't used primarily for architecture. I removed reference to “other technical photography” because I have no idea what it means; I have no objection to it's being restored if an adequate explanation can be provided. The first sentence in the second paragraph should probably be supported in any event; I know of many photographers who use 24 mm lenses for landscape work.
I don't especially like the description of shift, but it's by far the most common I found in about a dozen books I examined. I would prefer something to the effect of
But I'm not sure everyone would understand what the “line of sight” is, and this explanation isn't common in sources (Merklinger uses the term, but not in relation to translational movements). Howard Bond speaks of using shifts to point the camera, which I think is actually a pretty good description of what happens, but it strikes me as a bit informal for an encyclopedia. In any event, it's important not to say that perspective is controlled by shifting the lens, because that's not at all what happens—perspective is controlled by the orientation of the camera back relative to the subject. On a view camera, perspective is directly controlled by tilting or swinging the back; with a PC lens, this movement is emulated by reorienting the camera and using the shifts to adjust framing.
I think it may be worth adding a brief section on the convergence of parallel lines: they result from changes in magnification when parts of a subject are at varying distances from the camera, such as when it's pointed up at a tall building. Another consequence of the camera back not being parallel to the subject is that the subject is foreshortened. This important when perspective is corrected in software; two steps are usually needed: one to correct converging lines, and a second to correct the aspect ratio (removing the effects of foreshortening). There's a good Rodenstock article to support this.
The great remaining task is to address tilt/shift lenses, since they now represent almost all available lenses. Offhand, I don't see a good way to adequately cover them in this article without some major changes, and possibly making a mess of things. I'm consequently leaning towards a separate article to avoid some of the problems. As I've mentioned, there would necessarily be considerable duplication, and one significant question would be how to handle the Nikon PC-E lenses. They're tilt/shift lenses in everything but branding, but I'm sure some still use them only for the shift functions, especially the 24 mm. But I'm interested in ideas others might have. JeffConrad ( talk) 00:26, 28 March 2010 (UTC)
This article is terribly Nikon-centric in both terminology and examples. A tilt-shift-swing lens doesn’t and can never ‘correct’ perspective. Perspective comes, by definition, from a point of view, a position in space. Unless the camera moves, the perspective is the same, regardless of focal length or tilting, shifting, or swinging the lens. You can change the focal plane or crop from a different area of the image circle, but that doesn’t change perspective.
And statements like ‘Short-focus perspective-control (PC) lenses’ really don’t help. A macro lens would be short-focus, a wide angle lens has a short focal length. — Preceding unsigned comment added by Hugowolf ( talk • contribs) 00:43, 7 November 2013 (UTC)
![]() | This redirect does not require a rating on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||||||||||||
|
![]() | A fact from Perspective control lens appeared on Wikipedia's
Main Page in the
Did you know column on 28 May 2006. The text of the entry was as follows:
| ![]() |
The diagram is nice, but having actual images for both tilt, shift, and tilt/shift (vs. uncorrected). Cburnett 02:49, 20 October 2007 (UTC)
It would be good if someone could relate which (if any) digital SLR systems have compatibility with shift lenses, given how few there are. Or if none, simply state that fact. 82.10.108.49 ( talk) 21:53, 26 February 2008 (UTC)
Perhaps I’m being too fussy, but the description of the new Nikkor lenses was reading more like a Nikon brochure than an encyclopedia article. The buzzwords like “electromagnetic diaphragm” and “CMOS” apply equally to Canon, but they’re irrelevant to this article (as probably is “FX-format”, as well), serving only to clutter things up. I also question the statement that only the full-frame formats use the full capabilities of the lenses. It’s true that smaller formats (such as Canon’s 1.6 factor and Nikon’s 1.5 factor) don’t use the full image circles, but they afford some advantages as well (e.g., the shift is a greater fraction of the format size). Arguably, the greatest difference is the narrower ange of view, which sometimes is a problem and other times is an advantage. NPOV would seem to require comparable treatment of Canon and Nikon (and any other) lenses, and throwing in all the buzzwords forces the reader to wade through all sorts of material that has little real bearing on the substance of the article. JeffConrad ( talk) 04:46, 4 July 2008 (UTC)
I suppose there could be some point in mentioning the electromagnetic diaphragm on the PC-E Nikkor lenses if their preset operation on cameras other than the D3, D300, and D700 were contrasted with the mechanical preset operation of the PC Micro-Nikkor f/2.8D (non-E). I’ve added this to the article. If this information seems superfluous, get rid of it. I still recommend eliminating the last sentence in the paragraph; this article is about lenses, not camera bodies. JeffConrad ( talk) 07:41, 4 July 2008 (UTC)
I've moved the discussion of aperture control to a new section to lessen the clutter in describing available lenses. I'm not sure this material ultimately belongs here, although I'm also not sure where it does belong—perhaps in its own article. I'm a bit surprised that there is almost no mention of this in WP, but I suppose that, aside from PC/TS lenses, it's little more than a historical curiosity. JeffConrad ( talk) 04:26, 7 July 2008 (UTC)
The vast majority of lenses/adapters mentioned in this article include tilt functions as well as shift, so the current title is somewhat misleading. Should the page be moved and expanded accordingly? Currently, Tilt-shift lens redirects to Tilt-shift photography, which doesn't make sense (a lens is not a technique). JeffConrad ( talk) 02:18, 8 July 2008 (UTC)
Shouldn’t the term used in the gallery match the article title? Using “perspective correction” one place and “perspective control” in another just confuses the reader. Either term is workable, but the former may be preferable because it is more supplier neutral. JeffConrad ( talk) 21:49, 8 July 2008 (UTC)
This article is about perspective control but this is only half the story for a tilt-shift lens so why is it re-directed here? There needs to be some description of the tilt effect which is mainly to control focus. A tilt-shift article is needed. Unfortunately the tilt-shift photography article has morphed into an article on the photoshop technique. Kwenchin ( talk) 23:21, 28 February 2010 (UTC)
Perhaps once again I'm being too touchy, but this is starting to look more like a personal essay than an encyclopedia article. JeffConrad ( talk) 21:53, 31 July 2008 (UTC)
I was actually starting to think that the lens gallery is getting too large. For the most part, each lens looks pretty much the same. Maybe we could whittle this down to four that show the widest variety between the lenses and put the rest on Commons? howcheng { chat} 02:50, 1 August 2008 (UTC)
Can editor 199.227.143.21 provide a source for the availability of K-mount Zenitar tilt/shift lenses? I see MC Arsat versions of these lenses, on both the Arsenal site and the Hartblei site, but can find nothing on the Zenitar site. Whatever the source, the other available mounts should also be mentioned. JeffConrad ( talk) 07:44, 1 August 2008 (UTC)
There are serious compatibility issues, beyond those stated or implied in the article, with Nikon PC-E lenses and various Nikon camera bodies. Automatic aperture control is only available with the D300, D3, and D700 bodies; some other bodies support the electronic preset aperture control via the lens pushbutton, but apparently some do not. Ken Rockwell describes these problems in considerable detail; I've had only brief contact with a 24 mm PC-E lens, so I can't confirm his findings. On some camera bodies with built-in flash, the lenses cannot be rotated if maximum rise is employed; on others, it may not even be possible to set maximum rise without hitting the bottom of the prism housing.
Canon TS-E lenses provide automatic aperture control with any EF-mount bodies, but clearance of the prism housing is an issue on some DSLRs with built-in flashes.
To my knowledge, neither Canon nor Nikon have bothered to identify these incompatibilities. I'm not sure the responsibility falls to this article, but adding at least a general caveat might be a good idea. I'm lukewarm on including a link to Rockwell's article, because I've found his writings to be uneven in quality and even accuracy. Currently, though, I'm not sure what else is available, so perhaps a footnote mentioning an external link would point the reader to the article without the implication of endorsement. I know of no similar article that examines clearances on Canon DSLRs. JeffConrad ( talk) 21:29, 31 August 2008 (UTC)
yes, you lose resolution in the distant areas because they're recorded on a smaller area of film
I suppose it's possible to look at it this way, but it's mighty unusual statement. And even if one were to do so, this would be true for any lens; what in the world does it have to do with perspective control? And what is “lost depth of field due to the angle of the film/sensor plane to the subject”? Tilting a lens changes the orientation of the plane of focus and changes the shape and orientation of the depth of field, but there is no “lost” depth of field. And again, what does it have to do with perspective control? JeffConrad ( talk) 03:32, 1 September 2008 (UTC)
Perhaps I should have clarified my comment on the first issue: obviously, it's more difficult to resolve details on an object at great distance from the camera than it is to resolve those details on the same object close to the camera. What's unusual is to say that resolution in distant objects is “lost”; the resolution was never there. I cannot imagine anyone thinking that software perspective control would somehow improve resolution in distant objects; unless I've really misunderstood the intent, I cannot see why the statement I deleted belongs in this article. JeffConrad ( talk) 04:01, 1 September 2008 (UTC)
Most of this section really doesn't belong in this article; I originally added it only because there wasn't another good source to explain what an automatic diaphragm was. If there is no objection, I'll move most of this section to the Aperture article, leaving only material that specifically relates to tilt/shift lenses. JeffConrad ( talk) 00:14, 12 December 2008 (UTC)
The paragraph on using shift to negate the effects of motion blur in aerial photography is nearly incomprehensible as well as unsourced. Absent a reliable source, as well as a better explanation, I think this material should be removed. JeffConrad ( talk) 03:47, 4 September 2009 (UTC)
The linked article Tilt-shift miniature faking doesn't really have anything to do with the use of tilt; it's almost as if that article attempts to describe digitally faking a technique that doesn't really fake miniatures. In the second paragraph under Techniques, that article states
That statement is correct for two reasons:
The emphasis of that article is a bit difficult to discern, but it appears to describe a technique (e.g., Smallgantics that actually does simulate DoF that obtains from close-up photography. JeffConrad ( talk) 09:09, 7 September 2009 (UTC)
The section on lenses doesn't strike me as an advert; perhaps the sentence on the 35 mm PC-Nikkor could be slightly rewritten so it sounds less like bragging rights, but otherwise, I'm not sure how this section could be significantly changed and still adequately describe the lenses. IP editor made no comment, so it's impossible to address his objections; perhaps he doesn't understand the significance of things such as automatic diaphragms. In any event, unless the editor can indicate why the section isn't neutral, I recommend we remove the tag. JeffConrad ( talk) 23:02, 25 March 2010 (UTC)
I've updated the section to reflect current status (except for the Leica S 30 mm tilt/shift, for which I have no information). I've put the manufacturers in alphabetical order so that we don't imply that Canon and Nikon rule the world. I've also removed mention of the PC-Nikkor 35 mm; it's no longer available, and it's already mentioned in the lead section. Likewise, the image of the PC-Nikkor 35 mm is already included in the gallery.
JeffConrad (
talk)
02:06, 26 March 2010 (UTC)
I agree that the 1961 PC-Nikkor should be shown—I erred in saying the image in the gallery was of that lens. But the lens should be shown where it's discussed, not in the section on available lenses. And arguably at least as significant is the world's first tilt/shift lens, because all but one of the current available lenses includes tilt. Where do we stop? If we want to include every shift lens ever made, we should re-title the section or create a separate section for discontinued lenses. JeffConrad ( talk) 06:07, 26 March 2010 (UTC)
I agree with sizing the image to match the diagram. Though normal WP policy is “let the user decide”, common sense must prevail. Here, I think aesthetics dictate.
On a side note: the left-hand side of the top of the figure isn't correct—it should show the limit of the angle of view cutting off the top of the building. Any chance of getting this fixed?
Editor
90.195.131.21, who added the {{
advert}} tag, further explained the edit:
To an extent, I think the editor has a point. On the other hand, I think PC and TS lenses are somewhat different beasts, because they incorporate, to varying degree, special features unfamiliar to many photographers. And I also wonder if we ever could agree on which lenses are “notable”; for me, the list might include
A case might be made for including the original Nikon PC Micro-Nikkor 85 mm lens as the first “macro” TS lens, but I think its 0.5 magnification is simply an incremental gain from the Canon TS-E 90 mm lens's 0.29. Of course, others well might disagree.
Perhaps we could say something like “24 mm, 45 mm, and 90 mm PC-E lenses” rather than giving all the details. I'm not sure the maximum aperture is of interest to most readers, but I do think features such as automatic aperture control and independent rotation of shift and tilt are significant and merit mention.
Thoughts? JeffConrad ( talk) 22:35, 26 March 2010 (UTC)
I've cleaned up the lead section a bit, and updated a couple of comments to reflect the improvements in the image circles of recent lenses, and the availability of longer focal lengths that almost certainly aren't used primarily for architecture. I removed reference to “other technical photography” because I have no idea what it means; I have no objection to it's being restored if an adequate explanation can be provided. The first sentence in the second paragraph should probably be supported in any event; I know of many photographers who use 24 mm lenses for landscape work.
I don't especially like the description of shift, but it's by far the most common I found in about a dozen books I examined. I would prefer something to the effect of
But I'm not sure everyone would understand what the “line of sight” is, and this explanation isn't common in sources (Merklinger uses the term, but not in relation to translational movements). Howard Bond speaks of using shifts to point the camera, which I think is actually a pretty good description of what happens, but it strikes me as a bit informal for an encyclopedia. In any event, it's important not to say that perspective is controlled by shifting the lens, because that's not at all what happens—perspective is controlled by the orientation of the camera back relative to the subject. On a view camera, perspective is directly controlled by tilting or swinging the back; with a PC lens, this movement is emulated by reorienting the camera and using the shifts to adjust framing.
I think it may be worth adding a brief section on the convergence of parallel lines: they result from changes in magnification when parts of a subject are at varying distances from the camera, such as when it's pointed up at a tall building. Another consequence of the camera back not being parallel to the subject is that the subject is foreshortened. This important when perspective is corrected in software; two steps are usually needed: one to correct converging lines, and a second to correct the aspect ratio (removing the effects of foreshortening). There's a good Rodenstock article to support this.
The great remaining task is to address tilt/shift lenses, since they now represent almost all available lenses. Offhand, I don't see a good way to adequately cover them in this article without some major changes, and possibly making a mess of things. I'm consequently leaning towards a separate article to avoid some of the problems. As I've mentioned, there would necessarily be considerable duplication, and one significant question would be how to handle the Nikon PC-E lenses. They're tilt/shift lenses in everything but branding, but I'm sure some still use them only for the shift functions, especially the 24 mm. But I'm interested in ideas others might have. JeffConrad ( talk) 00:26, 28 March 2010 (UTC)
This article is terribly Nikon-centric in both terminology and examples. A tilt-shift-swing lens doesn’t and can never ‘correct’ perspective. Perspective comes, by definition, from a point of view, a position in space. Unless the camera moves, the perspective is the same, regardless of focal length or tilting, shifting, or swinging the lens. You can change the focal plane or crop from a different area of the image circle, but that doesn’t change perspective.
And statements like ‘Short-focus perspective-control (PC) lenses’ really don’t help. A macro lens would be short-focus, a wide angle lens has a short focal length. — Preceding unsigned comment added by Hugowolf ( talk • contribs) 00:43, 7 November 2013 (UTC)