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Image Circle Diameter Specifications for Leica M lenses


Assen Emilov

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Just off the topic but may be dastantly related!

If I say that largera the image circle better the corners and less vignetting.

Am I correct?

Up to a point, there are trade offs. If the image circle were really enormous, the lens would be larger, you might get flare and reflections from the shutter chamber, etc.

 

My sense of it is that Leica spends a lot of effort to tune the lenses for the format size and keep them compact. They might also do some masking internal to the lens to cut down the image circle in order to reduce internal reflections. They likely calculate image circle fairly tightly against the 43mm diagonal required for coverage.

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They likely calculate image circle fairly tightly against the 43mm diagonal required for coverage.

 

Even too tightly. Or more accurately, right to the edge of a slide mount.

 

I got a 90 Elmar-C to try out (the one from the Leica CL kits) - and it abruptly darkens the corners using a full 24 x 36 image @ f/4. Leica probably assumed CL users would get slightly cropped drugstore prints, or mounted slides, and never notice (and, Leica had to cram the lens into a "CL-sized" package).

 

Nice lens otherwise - Erwin Puts, (as mentioned) says it was the best Leica 90 available in its era (mid-1970s). Not quite as crisp as the slightly later Tele-Elmarit "thin" - but also avoids the flare from internal lens-barrel/camera chamber reflections!

 

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Even too tightly. Or more accurately, right to the edge of a slide mount.

 

I got a 90 Elmar-C to try out (the one from the Leica CL kits) - and it abruptly darkens the corners using a full 24 x 36 image @ f/4. Leica probably assumed CL users would get slightly cropped drugstore prints, or mounted slides, and never notice (and, Leica had to cram the lens into a "CL-sized" package).

 

Nice lens otherwise - Erwin Puts, (as mentioned) says it was the best Leica 90 available in its era (mid-1970s). Not quite as crisp as the slightly later Tele-Elmarit "thin" - but also avoids the flare from internal lens-barrel/camera chamber reflections!

 

attachicon.gifEMCvig.jpg

I have the same lens in M-Rokkor livery (early one, built in Wetzlar on the same production line), otherwise identical. Yes, wide open there's a bit of corner fall-off (not vignetting). Stop down to f/5.6 and it gets clean to the corners. I suspect in this case it was definitely due to the effort to make it small for the CL model and allow you to use the same filters. I've not found the corner fall-off objectionable for my photography, and otherwise just love the lens. It's made a LOT of excellent photos for me.

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Yes, wide open there's a bit of corner fall-off (not vignetting). Stop down to f/5.6 and it gets clean to the corners.

 

Out of curiosity, as I would guess that this fall off disappears as subjects focussed on get closer, at what focus distance does the fall-off disappear? I wonder if Leica also assumed that the lens would often be used for portraits and the fall off here would be negligible?

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Older non telephoto lenses 90 mm and up will cover 4x5.  90 2.8 Elmarit. 135 Hector.   They are listed in catalog as "long focus" compared to telephoto.  They also work well in close range.

 

Do not count on short lenses covering more than 24x35 mm at infinity.  Close up  will be more.

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