?? 125mm Fujinon-SW f/8 (ACTUAL Focal Length) ??

ic-racer · Dec 23, 2017

Old-N-Feeble said:
I'm a moron with regard to optical design. I guess I never took an interest in the subject. What I do wonder, is why Fuji opted for a retrofocus design, other than (maybe) an almost immeasurable decrease in fall-off at the corners.

It is not a retrofocus lens.

For example the Back Focal length on the Fuji 125/8, as pointed out is 83mm. This is actually SHORTER than the back focal length of the Schneider Super-Angulon 120/8 (a shorter focal length lens!).

In plain terms, the rear element of the Fuji 125 sits CLOSER to the film plane than the Schneider Super-Angulon 120mm.

Old-N-Feeble · Dec 23, 2017

Oh, okay. As mentioned... I'm not well-versed in optical design.

ic-racer · Dec 23, 2017

In the old days people learned photography in school, now day, the internet. Its good to download the spec sheets on all your large format lenses and get to know the numbers. This wiki has explanations of the numbers, though there may be a better resource out there also: https://en.wikipedia.org/wiki/Focal_length

E. von Hoegh · Dec 23, 2017

ic-racer said:
Another interesting tangent is that retrofocus design is not exclusive to wide angle. For example 8mm Reflex Bolex needs a lens with a Back Focal distance around 17mm to clear the shutter and viewing mechanism. So, the 13mm lens (long for the diagonal of the format) is a retrofocus.

And the '30s CZJ 50 mm for Contaxen Collapsible Sonnar is a moderately telephoto design.

Dan Fromm · Dec 23, 2017

Old-N-Feeble said:
I'm a moron with regard to optical design. I guess I never took an interest in the subject. What I do wonder, is why Fuji opted for a retrofocus design, other than (maybe) an almost immeasurable decrease in fall-off at the corners... and/or (maybe) to allow infinity focus with cameras which have longer minimum spacing between lens and film plane.

Yes, you're a moron. And easily led.

Super Angulons are not retrofocus. They are more or less symmetrical. Retrofocus lenses are best thought of as inverted telephoto lenses and are quite asymmetrical.

Nodda Duma · Dec 24, 2017

Yes, this is not a retrofocus design. It is a symmetrical type design (corrects aberrations by balancing the correction amongst the two lens cells in front of and behind the stop) with the rear cell having a longer focal length than the front.

Old-N-Feeble · Dec 24, 2017

Dan Fromm said:
Yes, you're a moron. And easily led.

Super Angulons are not retrofocus. They are more or less symmetrical. Retrofocus lenses are best thought of as inverted telephoto lenses and are quite asymmetrical.

You're an intelligent person, Dan. But often not very nice.

Dan Fromm · Dec 24, 2017

Old-N-Feeble said:
You're an intelligent person, Dan. But often not very nice.

True. You tossed me a big fat slow one and I just couldn't resist.

Old-N-Feeble · Dec 24, 2017

Okay... LOL!!

?? 125mm Fujinon-SW f/8 (ACTUAL Focal Length) ??

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