DaveFP wrote:
I am not a hard stop expert but I can share that my Zeiss lens manuals all say they don't provide an infinity hard stop to allow for the effects of temperature change.
That gives a plausible explanation as to why the newly designed Loxias never made it to the M mount. Temperature affects the behavior of ED/APD elements. The archaic RF focusing aid will not work well with the state of the art lenses with many APD elements.
Fred Miranda wrote:
If the hard stop focuses beyond infinity (like with your CV 21/3.5), it's not ideal but it's fine because at least a subject at infinity can be critically sharp.
The issue I had with my CV 35mm f/1.2 III VM copies is that the lens could never reach true infinity at the hard stop since it never reached true infinty. At first, I though Cosina optimized the hard stop for smaller apertures since the lens has focus shift but even at f/5.6 , a subject at infinity would be more in focus on the Sony compared to the Leica when comparing center crops.
If does not matter which camera you try as long as you have an adapter for the Voigtlander VM. So you could focus with your GFX or R5 on a subject at infinity distance (using high magnification to make sure), Then on your Leica, just focus the same scene using the hard stop and compare the center crops at 100%. If they are equal, that means your CV 35/1.2 III is indeed focusing correctly....Show more →
Follow-up on our 35 f/1.2 III infinity focus on M body discussion below.
NOTE FOR EVERYONE ELSE: This is not with the 35 APO!
Center crops from both systems @ f/5.6 below. M10-R focused to the hard stop, GFX 50R focused using high-magnification live view in the EVF.
Given the GFX 50R microlenses are so small and equal magnification is harder on the M10-R, I think these show the 35 1.2 III is correctly focusing to infinity on my M10-R.
realVivek wrote:
That gives a plausible explanation as to why the newly designed Loxias never made it to the M mount. Temperature affects the behavior of ED/APD elements. The archaic RF focusing aid will not work well with the state of the art lenses with many APD elements.
APD = apodization. Do you mean ASPH/aspherical? Leica and Voigtlander are doing fine making lenses with ASPH elements.
Ok, so like the glass Leica uses in the 50 Lux ASPH and others then.
Designed as a reference lens for the M-mount system, the black Summilux-M 50mm f/1.4 ASPH. from Leica is a versatile normal-length prime characterized by its bright maximum aperture and sophisticated optical design. Comprising eight elements in five groups, the lens features one aspherical element to reduce spherical aberrations and both anomalous partial dispersion and high refractive index glasses are used to control color fringing and chromatic aberrations for improved clarity. Additionally, a floating elements system is used to maintain consistent image quality throughout the focusing range, down to 2.3'. Additionally, the lens features a built-in extendable lens hood and is threaded to accept 46mm screw-in filters....Show more →
highdesertmesa wrote:
Follow-up on our 35 f/1.2 III infinity focus on M body discussion below.
NOTE FOR EVERYONE ELSE: This is not with the 35 APO!
Center crops from both systems @ f/5.6 below. M10-R focused to the hard stop, GFX 50R focused using high-magnification live view in the EVF.
Given the GFX 50R microlenses are so small and equal magnification is harder on the M10-R, I think these show the 35 1.2 III is correctly focusing to infinity on my M10-R.
Nice!
But f/5.6, I expect DOF to somewhat mask issues with focus but the real test is at f/1.2 (wide open). Do you have some of those?
The point that you are missing is that use of such glass (not just one element in an entire lens) as Cosina used in their FE version AL 65/2, 110/2 and 50/2 in generous amount will lead to temperature induced focus length shift. So, this is a drawback that the old RF system poses. This is in addition to the aperture induced focus shift (certain lens designs) that plagues that system.
highdesertmesa wrote:
Ok, so like the glass Leica uses in the 50 Lux ASPH and others then.
realVivek wrote:
The point that you are missing is that use of such glass (not just one element in an entire lens) as Cosina used in their FE version AL 65/2, 110/2 and 50/2 in generous amount will lead to temperature induced focus length shift. So, this is a drawback that the old RF system poses. This is in addition to the aperture induced focus shift (certain lens designs) that plagues that system.
Focus shift plagues many AF lenses as well, and it's something to stay educated about on a lens-by-lens basis and either adjust your focusing methods accordingly or buy other lenses not prone to focus shift.
And element glass materials and temp variations are not why Loxia was never made for M. Loxia was never made for Canon R or Nikon Z, either, so it's more about the huge market share Sony has.
I think we'd both agree, though, that focusing on any modern mirrorless is exponentially better than a rangefinder when it comes to accuracy, but most M users also have the option to use an EVF or the rear LCD.
As for temperature, you're overblowing the issue based on zero real-world experience using M. Or did you have an M and find it stopped focusing accurately at the equator and the poles? It's not like most M users are shooting street with a Noct at f/0.95 using the rangefinder, right? The entire M system is a throwback, and yes there are limitations but they don't seem to be hurting M users for what M users are using M cameras for
Fred Miranda wrote:
Nice!
But f/5.6, I expect DOF to somewhat mask issues with focus but the real test is at f/1.2 (wide open). Do you have some of those?
Is anything in sharp focus at f/1.2 on the 35 1.2 III at any distance? I'll give it a try, though
highdesertmesa, Unfortunately, you are being very presumptive about me. I own and use several M, LTM, etc cameras both film and a MM digital ( I bought it at that time only because it was the cheapest monochrome camera at that time). Had an Epson RD1s many moons ago.
Focus shift and RF: It is not overblown. Those who understand it and know it, know.
realVivek wrote:
highdesertmesa, Unfortunately, you are being very presumptive about me. I own and use several M, LTM, etc cameras both film and a MM digital ( I bought it at that time only because it was the cheapest monochrome camera at that time). Had an Epson RD1s many moons ago.
Focus shift and RF: It is not overblown. Those who understand it and know it, know.
Fred Miranda wrote:
Nice!
But f/5.6, I expect DOF to somewhat mask issues with focus but the real test is at f/1.2 (wide open). Do you have some of those?
[NOTE TO EVERYONE ELSE: This is not the CV 35 APO. We're having a separate conversation about the CV 35 1.2 III at Infinity on M bodies.]
Here's a comparison showing the 35 1.2 III at f/1.2 infinity hard stop on the M10-R versus best I could do with high magnification on the 50R.
M10-R was obviously overexposed given the 1/4000 sec. shutter speed + ISO 100 limit, so it's been recovered in post. The 50R was the electronic shutter around 1/11,000 sec. Camera was braced on the top of a fence for both.
The EVF quality on the 50R is not really up to the task for f/1.2 + infinity on a lens like this that's not really super sharp wide open at infinity. I took several and picked the best they were all about the same.
Normally with this lens at infinity in low light, I would probably choose to raise my ISO and go with f/2.8 as the maximum aperture. Even with my RF 50 f/1.2, which is very impressive wide open at infinity, I usually go no wider than f/2.
highdesertmesa wrote:
NOTE TO EVERYONE ELSE: This is not the 35 APO. We're having a separate conversation about the 35 1.2 III at Infinity on M bodies.
Here's a comparison at f/1.2 infinity hard stop on the M10-R versus best I could do with high magnification on the 50R.
M10-R was obviously overexposed given the 1/4000 sec. shutter speed + ISO 100 limit, so it's been recovered in post. The 50R was the electronic shutter around 1/11,000 sec. Camera was braced on the top of a fence for both.
The EVF quality on the 50R is not really up to the task for f/1.2 + infinity on a lens like this that's not really super sharp wide open at infinity. I took several and picked the best they were all about the same.
Normally with this lens at infinity in low light, I would probably choose to raise my ISO and go with f/2.8 as the maximum aperture. Even with my RF 50 f/1.2, which is very impressive wide open at infinity, I usually go no wider than f/2....Show more →
Thanks for this!
It does not quite reaches infinity at hard stop but it does better than all other copies I've tried. Consider yourself lucky!
Fred Miranda wrote:
Thanks for this!
It does not quite reaches infinity at hard stop but it does better than all other copies I've tried. Consider yourself lucky!
You think it's not reaching infinity here? I thought the M example looked sharper. I'll repeat the test when there is less atmospheric distortion, and maybe we can see any differences more clearly.
Or are you saying the lens doesn't reach infinity period on either?
highdesertmesa wrote:
You think it's not reaching infinity here? I thought the M example looked sharper. I'll repeat the test when there is less atmospheric distortion, and maybe we can see any differences more clearly.
Or are you saying the lens doesn't reach infinity period on either?
Yes, it does not quite reach infinity. I think the 50R crop is sharper.
Fred Miranda wrote:
Yes, it does not quite reach infinity. I think the 50R crop is sharper.
I'll give it another try when there's less heat distortion not because it will change anything, but it might make the difference more clear. I had a really hard time focusing the 50R. I may also try using the Visoflex on the M10-R in case the lens is reaching infinity before the hard stop (rangefinder does show alignment a hair before the hard stop).
Fred Miranda wrote:
Yes, it does not quite reach infinity. I think the 50R crop is sharper.
I casually checked looking through the Visoflex hard stop is as good as it gets at f/1.2, so I can rule out the lens reaching infinity before the hard stop. Thanks for the help walking me through the test(s). Glad I got a copy that's really close.
I'll give it a try, though 
