Talk:Parfocal lens: Difference between revisions

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Deleted external link 'Focusing trick can lead to blurry images'

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)[reply]

Opening sentence of main article may need a re-write/improvement

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)[reply]

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 I [http://en.wikipedia.org/w/index.php?title=Parfocal_lens&diff=521439527&oldid=521438556 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 [http://web.archive.org/web/20110708141415/http://www.cheapshooter.com/2007/09/25/focusing-trick-can-lead-to-blurry-images/ here] [[User:Katana|Katana]] ([[User talk:Katana|talk]]) 00:50, 5 November 2012 (UTC)
+== Opening sentence of main article may need a re-write/improvement ==
+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. [[User:TonyRony|TonyRony]] ([[User talk:TonyRony|talk]]) 13:28, 7 March 2014 (UTC)