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"It is almost impossible to stay in correct focus (as done manually by the focus puller)" — sorry, but this is false. Entire features have been shot on varifocal lenses since the introduction of Canon 5D mark II, including my own feature Kvadrat (film) which used a 24-105 mm" (I'm a director / DP). You may want to use the sources like ShotOnWhat, IMDb, or even the sources in Kvadrat (film) to correct this (look for varifocal Canon zoom lenses like the 24-70, 24-105 etc).
In other words: using a parfocal zoom is highly preferable in cinematography, but not necessary. A varifocal zoom lens can be used, including zooming while shooting, though requiring much more skill from the focus puller (you zoom and pull focus simultaneously). It's a question of comfort, not technical feasibility.
Anatoly IVANOV ( talk) 08:29, 19 October 2014 (UTC)
I deleted external links section, containing only 1 link to a now dead domain. The content was relevant but didn't add anything to the article IMO. Archive.org snapshot available here Katana ( talk) 00:50, 5 November 2012 (UTC)
Although I understand what the article is trying to say, as currently written (A parfocal lens is a lens that stays in focus when magnification/focal length is changed.), the opening sentence may be incomplete at the very least, and possibly incorrect.
To make my point, see the Ehow.Com entry entitled 'Why Is It Desirable That Microscope Objectives Be Parfocal?'. Paying particular attention to the paragraph 'Determining Parfocality,' note that practicality dictates that images viewed through a parfocal optical system must first be brought into focus by viewing the subject using the system's maximum magnification. Thereafter, if the optical system is indeed parfocal, then changing the focal length to lesser magnification levels will continue to yield a focused image.
So ... While the current opening sentence may technically be correct, without mentioning how optimal focus is achieved, this is the reason I consider the article's opening sentence incomplete. TonyRony ( talk) 13:28, 7 March 2014 (UTC)
Lots of text on what they are and who uses them, no information on how the optics works under the hood!
Can anybody help fill that out? I want to know more. Miserlou ( talk) 21:31, 26 August 2020 (UTC)
![]() | This article is rated Start-class on Wikipedia's
content assessment scale. It is of interest to the following WikiProjects: | ||||||||||||||||||||
|
"It is almost impossible to stay in correct focus (as done manually by the focus puller)" — sorry, but this is false. Entire features have been shot on varifocal lenses since the introduction of Canon 5D mark II, including my own feature Kvadrat (film) which used a 24-105 mm" (I'm a director / DP). You may want to use the sources like ShotOnWhat, IMDb, or even the sources in Kvadrat (film) to correct this (look for varifocal Canon zoom lenses like the 24-70, 24-105 etc).
In other words: using a parfocal zoom is highly preferable in cinematography, but not necessary. A varifocal zoom lens can be used, including zooming while shooting, though requiring much more skill from the focus puller (you zoom and pull focus simultaneously). It's a question of comfort, not technical feasibility.
Anatoly IVANOV ( talk) 08:29, 19 October 2014 (UTC)
I deleted external links section, containing only 1 link to a now dead domain. The content was relevant but didn't add anything to the article IMO. Archive.org snapshot available here Katana ( talk) 00:50, 5 November 2012 (UTC)
Although I understand what the article is trying to say, as currently written (A parfocal lens is a lens that stays in focus when magnification/focal length is changed.), the opening sentence may be incomplete at the very least, and possibly incorrect.
To make my point, see the Ehow.Com entry entitled 'Why Is It Desirable That Microscope Objectives Be Parfocal?'. Paying particular attention to the paragraph 'Determining Parfocality,' note that practicality dictates that images viewed through a parfocal optical system must first be brought into focus by viewing the subject using the system's maximum magnification. Thereafter, if the optical system is indeed parfocal, then changing the focal length to lesser magnification levels will continue to yield a focused image.
So ... While the current opening sentence may technically be correct, without mentioning how optimal focus is achieved, this is the reason I consider the article's opening sentence incomplete. TonyRony ( talk) 13:28, 7 March 2014 (UTC)
Lots of text on what they are and who uses them, no information on how the optics works under the hood!
Can anybody help fill that out? I want to know more. Miserlou ( talk) 21:31, 26 August 2020 (UTC)