Refocusing for IR photography using Nikon ED glass lenses.

[Rolland Rainbow Elliott <X93ELLIOTT1@xxxxxxxxx>]

I also read the following in Theresa Airey's Book, Creative Printmaking:
"IR radiation doesn't focus on the same plan as visible light, so you must
roate the lens barrel slightly forward to readjust your focus to the IR
compensation mark.........But with some of the new autofocus (AF) lenses,
such as most of Nikon's AF lenses, this isn't necessary (the exception:
Nikon's 80-200mm f/3.5-5.6 D lens).  through the use of extra low dispersion
(Ed) glass, these lense can pull all the wavelengths into focus, including
the infrared ones."

I know the Nikkor 80-200mm ED f/2.8D AF lens also needs to be refocused
because it has an IR refocus mark.  So obviously the above statement is
rather vague.
My question is "Which Nikkor ED lenses have you used that do not require an
IR focusing adjustment?"
I'm sure other listmembers would find this information interesting.

Another question:  "Is there any relationship between the focal length of a
lens and the need to perform an IR focusing adjustment?"  I ask this because
the brochure that came with my Sigma 70-210 f/2.8D AF APO zoom lens  says
that IR focusing adjustment is only needed at the short (70mm) end of the
lens.

Thanks, Rolland
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End of Infrared-Digest V0 #272
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