>In article , Winsor Crosby <wincros@xxxxxxx> wrote
>>My impression was that IF lenses arose out of the need to reduce to size
>>and load on the tiny motors for autofocussing cameras and lenses.
>
>Nope - I was designing systems with IF lenses before autofocus was ever
>available.
>
>> It did
>>not have_anything_ to do with an inherent superiority of one system to
>>produce an excellent image at the film plane.
>
>True - but it had a lot to do with ensuring that the lens did not get
>contaminated during extended periods of naval and airborne operation -
>IF permitted a completely sealed lens design.
>
>>It was an engineering
>>solution to the limitations of batteries and electrics.
>
>In the commercial SLR instance it was a solution waiting for the problem
>to arrive - IF lenses were in common use long before AF.
>--
>Kennedy
Sorry, Kennedy, sloppy writing. You keep us on our toes. I did not mean to
imply that IF lenses were invented for SLRs. I was intending to talk about
the use of IF lenses on the kinds of cameras we usually talk about and all
I have in this case is my recollection with a long interest in amateur
photography. It does not surprise me that IF lenses were in use for
specialized purposes such as military or scientific applications. Leitz was
using them in their binoculars before autofocus became the hot new thing.
With roof prisms, they were an elegant solution, although they had trouble
with not focussing closely. I believe that Zeiss, instead, pressurized
their binoculars which was touted as a solution for the contamination
problem.
Now if you could do that with interchangable lenses....
Winsor
Winsor Crosby
Long Beach, California
mailto:wincros@xxxxxxxxxxx
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