Re: Medium format (was: plastic sheets

[Jim MacKenzie <aa279@xxxxxxxxxx>]

On Sun, 6 Jul 1997, Jaap Los wrote:

> I own a Nikkor 2.8/80-220 mm ED zoomlens, a beauty. I understand from
> your mail messages, that I don't need to refocus this lens for IR
> photography?? Mind you, there is a special IR focus indicator on this
> lens, meaning, that a refocus is needed. Am I right? Or will the
> ED-element sufficiently correct also for IR? Is there any difference for
> using HIE, Konica 750 or SFX200/Agfa200 as regards to IR focus
> correction?

Your zoom probably has too many elements and the glass elements affect 
the focus point of infrared light.  The fixed-focal-length Nikkors with 
ED glass focus IR to the same point as visible light so no focus 
correction is needed.

If there is an IR mark you should use it.  I'm sure that with a lens like 
the 80-200/2.8, it was just too hard to make IR focus to the same point 
and keep the visible light quality to a maximum.

Jim

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End of Infrared-Digest V0 #110
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