Makten wrote: rdeloe wrote: Makten wrote:
The tiny Olympus OM 100/2.8 is somewhat usable on GFX. Illumination of the sensor is mostly fine, but there is a fair amount of backwards curvature of field, and smearing of the corners even stopped down. However, considering the minimal size I can see some use for it, especially for semi-close shots wide open.
First one was at f/4 and the second is wide open. Edit: Both are JPG SOOC with Provia and everything set to "zero", which might say something about general contrast and colors.
I'm surprised the Olympus OM 100/2.8 is showing that behaviour. I had to change the spacing between the cells on on several lenses to get them to perform properly on GFX (due to that thick cover glass). But all the affected ones were shorter than 80mm and had rear elements that extended past the mounting flange. Among the Mamiya N lenses, the 43mm and 65mm needed adjustment, but the 80mm didn't; notably the rear cell of the 80mm does not extend beyond the flange, but the 65mm and 43mm do. Ditto my Mamiya G 50mm, which also improved considerably by closing up the cell spacing.
Well, it's an absolutely tiny lens, not much larger than your average 50/1.8 from the seventies. I suppose the exit pupil is pretty far back or something. There seem to be very few lens elements in the design too, so maybe not comparable to similar lenses.
Interesting idea with moving the groups in a lens. With "rear cell", do you mean everything behind the aperture?
I used to have that lens and liked it a lot. I shot it on APS-C as part of a tilt-shift kit.
I didn't mean to give you false hope that the cell spacing is adjustable in that OM 100/2.8 lens. This procedure is easiest with lenses mounted in shutters, like large format lenses. I use the Schneider-Kreuznach APO-Digitar 35mm f/5.6 L-88 (predecessor of the XL-110) and a Schnedier-Kreuznach APO-Symmar 100/5.6. The 35mm was unusable without closing up the cell spacing. I moved the cells from the APO-Symmar into a different housing and had to fine tune the spacing (but I'm not sure if the cells ended up closer in that case).
The other lenses that I've done are Mamiya N 43mm f/4.5 L, Mamiya N 65mm f/4 L, and Mamiya G 50mm f/4. The 43mm had a thick shim behind the rear cell that I replaced with a thin one, and the 65mm and 50mm had shims under the front cell.
I don't think this is going to work with lenses that have floating elements.
Importantly, doing this is far from ideal because now the lenses won't work properly on any other system. For example, if I switched to a Hasselblad CFV 100C back, I'd have to re-shim them all back to where they were originally.
there's a shim behind the front or rear cell. If there's not shim, then they're as close together as they can come.
May 24, 2024 at 02:29 PM
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