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I have nothing against reviewers' opinions but as long as Leica does not publish those OTF diagrams or others i will go on using their MTF charts to get objective informations personally. YMMV.

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9 hours ago, jaapv said:

... However, MTF curves are a limited tool, measuring contrast response in one plane of focus only. You even struggle comparing between brands, let alone formats. OTF diagrams are a bit more useful, but complicated and expensive to make. In the end the only useful way to compare lenses is to look at photographs. Failing that, read trusted reviewers ( the Sean Reid and Erwin Puts type) and base your conceptions on those.

Now I am intrigued.  WHAT is an OTF?  And where do you encounter them?  Both Sean Reid and Erwin Puts have strong and demonstrated biases, but at least they are consistent over time.  I'm not sure that "trusted" is a complete description, since you have to get to know them before using their advice.

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The Wikipedia article is quite good but very technical. When using three-dimensional OTF one could describe the performance of a lens in three dimensions.  That, however, is far too complicated  for lens reviewing.

In "Leica Lens Practice" Dennis Laney describes a method of representing the OTF in clear box diagrams,. which would be very informative and useful for lens comparisons. It would, for instance, give a direct representation of astigmatism.

However, as he notes, the method was too complicated for simple magazine tests and never caught on. Nowadays, with adequate computing power, it would be possible, but reviewers are stuck on MTF curves, which are a reasonably good derivate of the OTF, but tell us nothing about the performance of the lens outside a single plane of focus, and nothing about concepts like macro contrast, OOF rendering and Coma. Vague concepts like rendering and sharpness cannot be described at all by MTF curves. Precisely parameters like those are  what photographers are looking for when judging a lens.

Another thing is that it is hard to compare MTF curves between formats and even different brands. Puts notes in his old Lens Compendium -please don't press me for the page number; I'm quoting from memory- that one should not compare for instance Leica and Zeiss MTF curves because Leica's are computer-generated from the design and Zeiss' are measured from the actual lenses (at least, back when the book was written I suppose, things may have changed by now)

As you imply, the thing to do is to stick to reviewers who are transparent and consistent in their methodology, like Puts and Reid, and avoid taking the Huffs et al.of this world too seriously, entertaining as they may be, and best of all, trust the evidence of your own eyes. Judge images by the various lenses, preferably those that come close to your own style and subjects. Better still, rent or borrow and try out.

Relying on MTF curves is bound to end in forum posts like "the rendering is too clinical" "The Zeiss lens is sharper", etc.  😢 ;)

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Wikipedia has 13 entries for OTF, including switchblade knives (the blade comes "out the front") and a cricket penalty, but I will read about Optical Transfer Functions.  I think this is the way to think about the increased apparent sharpness that Peter Karbe is describing when he says that the falloff in sharpness away from the in-focus plane at f/2 in his newest designs is like what we used to see in f/1.4 lenses.  And it is not depth of field as conventionally tabulated, but no longer presented in technical specifications.

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Frankly we cannot compare full frame MTF (3.4/135mm) with APS-C one’s (55-135mm) 

and even comparing one’s MTF with the other. It is a draw. 

BTW have you notice the stellar MTF performance of the 55-135 at 55 and 85 ? Actually way better at 85mm (128mm) than the 3.4/135mm on a full frame M   

And in real life the APO-Vario is much more practical than the APO-Telyt. Which is not fast at all with f/3.4. Almost same weight. Too long minimum focusing distance 1.5m ! And a very expensive price tag. And it is almost useless with a digital M without Visoflex. 

So no point to defend this M lens. 

And no sardine here. 

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I saw that article too and it was funny, yes mainly funny. A camera as a life-style-product, a camera as a statement (of what-ever). Expensive lenses like the 095/50 as a sign of wealth (I had the combo during a Leica-seminar, its heavy, simply heavy). What a non-sense. A world of empty luxury.

Once I had a M and I was so proud, I had some extraordinary lenses and my little daily fights with correct focus, when I change lenses I had my little fight with dust. I could not say that my pictures were better, but I was so proud. Now I am grown up.

Cameras are technical tools, everything else is pseudo-philosophical blabla. And the CL is a perfect technical tool, with a great EVF, a set of very nice lenses, it is fast and when using an adapter open for almost every lens of this planet.  A camera is a technical tool to realize the picture you create within your head, since I have the CL I have a kind of explosion of ideas. Why? Because it is possible with this tool. Macro, tele, super-wide, vintage lenses.......

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On 1/5/2019 at 3:14 PM, nicci78 said:

Frankly we cannot compare full frame MTF (3.4/135mm) with APS-C one’s (55-135mm) 
and even comparing one’s MTF with the other. It is a draw. 
BTW have you notice the stellar MTF performance of the 55-135 at 55 and 85 ? Actually way better at 85mm (128mm) than the 3.4/135mm on a full frame M   
And in real life the APO-Vario is much more practical than the APO-Telyt. Which is not fast at all with f/3.4. Almost same weight. Too long minimum focusing distance 1.5m ! And a very expensive price tag. And it is almost useless with a digital M without Visoflex. 
So no point to defend this M lens. 
And no sardine here. 

Rather the frog that wished to be as big as the ox then :D. Just kidding but the radius of the sensor is about 21mm on FF cameras (43.27mm diameter divided by two) whereas it is only 14mm on APS-C cameras (28.37mm divided by two). Reason why FF lenses show their so-called "sweet spot" with crop cameras i.e. between 0mm and 14mm on the Leica charts below.
https://photos.smugmug.com/photos/i-jdcz8mQ/0/8fdc86d2/O/i-jdcz8mQ.jpg

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Unfortunately APO-Telyt 135mm is still not better than APO-Vario 55-135. Still a draw. Just more astigmatism, but it is not relevant in real life. And according to MTF  55-135 is still sharper in center.

Same critics still stand about the M 3.4/135mm though

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