@dab : Thanks for the collection of old Leica advertisements! That's really fun!
An 'anastigmat' lens is a lens optical design designed to eliminate astigmatism (that is: prefix "a
👎" meaning without, "astigmat" as short for astigmatism) and allow proper focusing of points on the focus plane. First such lens in production was evidently from Zeiss in about 1890. The adoption of the term as the name of a lens as "Anastigmat" would certainly cause some confusion...
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(I just bought my first digital M - the M240 - and am frankly shocked at how hard it is to focus a 135mm lens accurately. I've never struggled like that on a IIIf or IIIg. No wonder people don't like them!)
Hmm? I don't recall the M typ 240 viewfinder being much different from my M10 Monochrom or M10-R ... I pulled out my beloved and ancient Hektor-M 135mm f/4.5 and did some tests, focusing first with the rangefinder and then with the Visoflex 020 and focus assist magnification on several different objects around my condo and outdoors. I guess my eyes are still up to the task with the RF and such a long lens as I was able to achieve perfect critical focus 19 times out of 20 with the RF, however the Visoflex 020 with magnification makes it much faster to focus, and I hit 20 out of 20 that way.
(I did notice once upon a time when the M9 was freshly sold and I had just received the M-P typ 240 that the latter's viewfinder was actually much crisper in the RF patch compared to my M9... but that may have been simply a issue with my M9's rf system .. probably needed a tiny bit of cleaning or adjustment.)
Of course, fitting the same lens to the new-to-me M6TTL 0.85x body makes focusing the RF faster and I think more consistent, but I'm unwilling to sacrifice a roll of film and an hour's processing work to confirm it.
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But yes: focusing a 135mm lens with a rangefinder can be a bit difficult, and I figured out that this was made my dear old friend Don descry the Hektor 135mm as being "an unsharp piece of junk!" compared to the Nikon F and 135mm lens he replaced his M3 + Hektor with. My Hektor 135 is exactly the same lens he had and returns delightfully sharp photographs, which amazed him, but then I have the benefit of Live View and the Visoflex 020 to ensure critical focus.
I don't have an LTM version of the Hektor (or any other lens past 50mm ...did once upon a time...) to test focusing with the Leica IIIc body's rangefinder, but its 1.5x magnification should give focusing accuracy comparable to the M6TTL 0.85x (trading of a bit of RF baseline with more magnification). I've been thinking of finding a nice 90mm lens for it, but doubt I'd use it enough.
G