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Re: Eclair Cameras: Kinoptik Apochromat 25mm f2 for Cameflex / ACL?

--- CJ Schepperstop <cjs@sound.net> wrote:
The diameter of the glass optics suggest that it is
for 16mm.  The lens
vignettes the image on 35mm academy aperture.

---  You shouldn't make that assumption because of
it's size.  Compare it with a 28mm Schneider for a
Arri IIB/IIC.  Or a 25mm Baltar or even an old non
retro-focus 24mm Cooke Panchro.
The Nikkor is a retro-focus design. So it's basically
a longer lens with a negative front section added on
to reduce the image size/ reduce the focal length like
an aspheron attachment.

The f/stop is determined by dividing the focal length
(f) by the diameter of the lens, therefore the glass
on the Kinoptik should be about 12.5mm in diameter.
The 25mm Kinoptik design is the same as 50mm and the
75mm Kinoptiks, just scaled down.  The light falloff
the 25mm is also scaled down.  Where as the Nikkors
diameter and falloff are those of the back section.
The larger area of falloff is one of the advantages of
a retro-focus design, but it pays for it in physical
size.   You'll find a similar situation with wide
angles on 35mm range finder cameras.

One of the claims about the original late 40s Cameflex
was that it could accept a 25mm lens, while the
Arriflex could only go as short as 28mm.
I used to work at a rental house that had two
Schneider 10mm Cinegons.  One fit onto an Arri 16BL,
the other didn't.  The difference between the two was
that the older one had a flange around the rear
element which wouldn't clear the BL mirror, the newer
one didn't have the flange so it cleared the mirror.
My guess is that there's that sort of minor design
difference between older and newer Cameflex models and
the Kinoptiks.

-sitting around very bored, but still in TohoScope,

--- El Pedante

PS: spell check Cinegon.

I appreciate your comments.


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