DavidBM
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Steve Spencer wrote:
David,
I very much appreciate your input, but I think you are wrong about the Leica M 90 f/2 AA. Leica does say, "Brilliance and resolving power are already outstanding at full aperture." So it seems like very high performance wide open was a specific goal when this lens was developed. Here is what Erwin Puts says about the lens, "At full aperture (2.0) the lens exhibits a high contrast image with extremely fine details rendered with excellent clarity and contrast. On axis (center) and in the field (outer zones) and extending to the very corners, minuscule details are re- corded impeccably." The MTFs also support this very high performance wide open. In the centre this lens has about 95% contrast at 10 lp/mm, 85% contrast at 20 lp/mm, and 65% contrast at 40 lp/mm. There is a gradual drop of about 10% contrast as you move to the corners, but his is very high performance. Sure the new Voigtlander 50 f/2 APO is slightly better, but not a huge amount better and we have had 20 years since the Leica M 90 AA was designed. I see no reason that a Voigtlander 85 or 90 APO couldn't be of similar size to the Leica M 90 AA....Show more →
Hi Steve
Sure I don't disagree that the APO Summicron is terrific even wide open, and maybe it's unnecessary to go for higher MTF40 than the APO summicron, but as I read the MTF chart the APO summicron is sitting in the early sixties centrally, falling off gently to 50% in the corners for MTF 50.
This is, indeed, great performance.
But the Lox 85 sits on 70% for most of the field down to just below 60 in the corners (admittedly at f2)
And the CV APO Lanthar 50 promises damn near 80% wide open for most of the field, dropping gracefully to 60 at the very edges of the field.
Is this extra performance visible in images? Mostly not, I'm guessing.
Is caring about this measurebating, as some call it? Maybe. I sit on the fence.
Would I prefer a design which is small, has f2 performance like the Summicron and gets crazy good rather than just superb one stop down over a bigger design that has 5-10% more MTF 40 wide open? Yes I would.
But my sole question was how likely it is that we'll get a smallish Apo Lanthar 2/90 given that they want it to perform like the existing one. I guess I still think that's unlikely: though I'd prefer if they reduced the intended quality indiscernibly less and shrank it.
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