Actually, if the subject or plane of focus is 1-2m and the background edge is 5-9m, I see the same thing on my M-240, this while the center at 10m + is out of focus. Same results on the Z 7, especially if resampled to 24mp (jpg only, no baked in presets).
Apr 03, 2022 at 08:56 AM
Steve Spencer Offline • • • • • • • Upload & Sell: On
mapgraphs wrote:
Actually, if the subject or plane of focus is 1-2m and the background edge is 5-9m, I see the same thing on my M-240, this while the center at 10m + is out of focus. Same results on the Z 7, especially if resampled to 24mp (jpg only, no baked in presets).
Well I don't think there is any question whatsoever that the lens performs better on a thin sensor camera than on the the stock Z7 on that Lars and I most certainly don't disagree. The results that Fred reports earlier in the thread here: https://www.fredmiranda.com/forum/topic/1704868/1#15621733 with a Sony camera is almost exactly what I find with the stock Z7. I actually find almost no differences with over a dozen lenses that I have compared between a Sony body and the stock Z7. They seem to have a very similar sensor stack.
Probably should add that I haven't noticed this effect with the earlier Ultron f/1.9 LTM on the M-240. Not saying the field curvature effect with the LTM version doesn't exist on the M-240, I just don't recall seeing it. I haven't used version I of the f/2 in enough situations to be able to make a comparison.
mapgraphs wrote:
Actually, if the subject or plane of focus is 1-2m and the background edge is 5-9m, I see the same thing on my M-240, this while the center at 10m + is out of focus. Same results on the Z 7, especially if resampled to 24mp (jpg only, no baked in presets).
What exactly are you seeing, when you say you see the same thing?
With focus at about 2 meters and the background about 5 meters away, I am seeing an out of focus background all over with the Z7, however, slightly less blurred in the side and corner than with the Z6UT.
mapgraphs wrote:
Probably should add that I haven't noticed this effect with the earlier Ultron f/1.9 LTM on the M-240. Not saying the field curvature effect with the LTM version doesn't exist on the M-240, I just don't recall seeing it. I haven't used version I of the f/2 in enough situations to be able to make a comparison.
It's very easy to test this. Find a flat infinity subject that extends from center to the very corners. Focus the subject at center with the lens wide open. Do the same procedure with your Nikon (lens adapted) and Leica M240. Then compare the mid-zone and corners of the frame. You will see that the Nikon images are not as sharp as the Leica's due to induced field curvature.
Steve Spencer wrote:
Well I don't think there is any question whatsoever that the lens performs better on a thin sensor camera than on the the stock Z7 on that Lars and I most certainly don't disagree. The results that Fred reports earlier in the thread here: https://www.fredmiranda.com/forum/topic/1704868/1#15621733 with a Sony camera is almost exactly what I find with the stock Z7. I actually find almost no differences with over a dozen lenses that I have compared between a Sony body and the stock Z7. They seem to have a very similar sensor stack.
Agree. Before I got the Z6 modified, I also had the a7II. I tested all my M mount lenses on both cameras and found that the Z6 was generally slightly better, but nothing more. This could also be because the Z6 has an BSI sensor while the a7II has the older type. Fred's comparison roughly looks like my tests with the Z7 and 28mm Ultron II.
This is not strong field curvature behavior in my book, but certainly visible when the corner will show you what's going on. My impression is that the field with 28mm Ultron II on Nikon Z7 is mostly mildly outward curved, except for the extreme corners, where it bends more noticeably. For images where you have blue sky or generally something undifferentiated in the extreme corners, it won't be a problem.
Fred, what I was trying to describe is that the field curvature effect is visible on the M-240. As you know, the curvature plane changes with the point of focus and with this lens when you have the perfect alignment of objects at various distances, you get the same effect on this "thin" sensor as is displayed on a camera with a "thick" sensor. I think I have a good idea about how the well and micro-lens designs impact inherent field curvature, and I'd say these designs have as much impact on sensor output as the thickness of the cover glass...
I am planning to do some tests beyond what I posted previously but from usage so far, I have a good feel for what the lens is going to do on my M-240, in a variety of situations.
mapgraphs wrote:
Fred, what I was trying to describe is that the field curvature effect is visible on the M-240. As you know, the curvature plane changes with the point of focus and with this lens when you have the perfect alignment of objects at various distances, you get the same effect on this "thin" sensor as is displayed on a camera with a "thick" sensor. I think I have a good idea about how the well and micro-lens designs impact inherent field curvature, and I'd say these designs have as much impact on sensor output as the thickness of the cover glass...
I am planning to do some tests beyond what I posted previously but from usage so far, I have a good feel for what the lens is going to do on my M-240, in a variety of situations.
It's not just induced field curvature but astigmatism as well. The thicker stack affects lenses in a way they can't recover even when focusing on a specific area of the image field. I don't remember seen much field curvature with the CV 28mm f/2 II at infinity but it does not mean it does not happen at close/mid-distance. I will test it out but usually 28mm lenses show some outwards field curvature at close/mid distance. The exception being the Zeiss 28/2 Distagon with inwards FC.
Photo cross posted in the Sony FE Image Thread and taken at 12:23 PM.
Looking across a portion of Termini Immerse (Termini) toward the mountains behind; Mount San Calogero can be seen at the left side of the image behind the city. Termini Immerse is about 22 miles from Palermo.
Hand Held relying on Camera IBIS? or tripod mounted, A7rII Kolari Vision UT sensor modified camera and Voigtlander 28mm f2 Ultron II VM lens; silent shutter.
ISO 100, F8?, 1/250 Second.
Exposure Corrected -0.09 Stops.
March 14, 2022
At Termini Immerse (Termini), Sicily, Italy.
Photo cross posted in the Sony FE Image Thread and taken at 3:17 PM.
Looking at a farm with snow at/near the the intersection of Loch Valley Road and Stony Ridge Road.
Tripod mounted A7rII Kolari Vision UT Sensor modified camera and Voigtlander 28mm f2 Ultron II VM lens; silent shutter.
ISO 100, f8?, 1/640 second.
Exposure Corrected +0.26 Stops.
January 31, 2022
Near the intersection of Loch Valley Road and Stony Ridge Road, New Tripoli, PA.
Photo cross posted in the Sony FE Image Thread and taken at 1:55 PM.
Looking at the Pinocchio Shop.
Hand Held relying on Camera IBIS, A7rII Kolari Vision UT Sensor modified camera and Voigtlander 28mm f2 Ultron II VM lens; silent shutter.
ISO 100, F8?, 1/100 Second.
Exposure Corrected +0.18 Stops.
Photo cross posted in the Sony FE Image Thread and taken at 12:18 PM.
Looking at the Central Courtyard of the Pompeii Archeological site. Taken on this heavily overcast, rain threatening day.
Hand Held relying on Camera IBIS, A7rII Kolari Vision UT Sensor modified camera and Voigtlander 28mm f2 Ultron II VM lens; silent shutter.
ISO 200, F8?, 1/125 Second.
Exposure Corrected +0.09 Stops.
Fred Miranda wrote:
Ahwahnee restaurant, Yosemite
Leica M10-R + Voigt 28/2 II
PS: My lens is coded to the Leica 28/2 cron.
Thanks for all the tests and samples. Are you getting perfect infinity focus at the hard stop on your M10-R with this lens? The CV 21 3.5 I tried last year focused past infinity on my M bodies, so I've been leery to try another small CV wide angle.
Unfortunately it won't help buying a Leica brand lens. They are also varying in my experience. The 28mm Summicron-M Asph II that I had went far beyond infinity on a M 240 I tried it on. The 90mm Apo-Summicron-M as well as Elmarit-M and Summarit-M I had also had different infinity points too. Maybe one of the four was spot on, but the three others would be off then.
highdesertmesa wrote:
Thanks for all the tests and samples. Are you getting perfect infinity focus at the hard stop on your M10-R with this lens? The CV 21 3.5 I tried last year focused past infinity on my M bodies, so I've been leery to try another small CV wide angle.
LarsHP wrote:
Unfortunately it won't help buying a Leica brand lens. They are also varying in my experience. The 28mm Summicron-M Asph II that I had went far beyond infinity on a M 240 I tried it on. The 90mm Apo-Summicron-M as well as Elmarit-M and Summarit-M I had also had different infinity points too. Maybe one of the four was spot on, but the three others would be off then.
I exchange any lens that doesn't hit infinity at the hard stop (or return for a refund if I can't get a correctly-calibrated copy after a few tries). Without perfect hard stop at infinity, it removes one of the main reasons I choose to use an M camera.
highdesertmesa wrote:
I exchange any lens that doesn't hit infinity at the hard stop (or return for a refund if I can't get a correctly-calibrated copy after a few tries). Without perfect hard stop at infinity, it removes one of the main reasons I choose to use an M camera.
At least 99% of my pictures are taken in the 0.5-5 meter range so I only really care about accurate rangefinder calibration. How is hitting infinity at the hard stop crucial for your use case(s)?
genji wrote:
At least 99% of my pictures are taken in the 0.5-5 meter range so I only really care about accurate rangefinder calibration. How is hitting infinity at the hard stop crucial for your use case(s)?
I shoot a lot of landscapes that are mostly sky with just a bit of land at the bottom that's at infinity. I also shoot a lot of landscapes that when focus is set to infinity and aperture is at f/5.6 or f/8, I get everything in the shot in focus. I prefer to just hit the hard stop and shoot. If I want to have to spend time focusing every shot to perfection at infinity, then I'd rather just use an AF camera system. It's also just an OCD thing. If it's possible for a lens to be perfectly calibrated to hit infinity at the hard stop, then that's how I prefer it to be.
My point is that it's not a Voigtländer (brand) issue, it's a system issue.
My understanding is Leica at least tries to correctly calibrate every new lens to hit infinity at the hard stop on an M body, though, right? And outliers can be adjusted? I just wasn’t sure about these little CV retro wide angles since my CV 21 3.5 has been the only M lens I ever owned that hit infinity quite a bit before the hard stop. Returned it since I heard it was common for that lens.
I think all M lens manufacturers make an effort to get the infinity point right. The problem is that with wide angle lenses, less than one tenth of a millimeter is enough to blur the image.
With rangefinder cameras you have both the mount to sensor/film distance and the rangefinder mechanism that may be slightly off, and on the lens both parts should be precisely made too. If your camera or lens is just slightly off in one of these two factors, you will have problems with getting (infinity) focus spot on - especially with very wide angle lenses. Infinity focus could be right at the hard stop, while the RF shows it's a bit off, or the RF is right, but infinity focus isn't at the hard stop. Both will be annoying, but getting the RF right should be the priority.
If the lens is otherwise fine, shimming the mount or adjusting the RF coupling may be a more constructive approach. That's why it's great idea that 7Artisans came up with: user adjustment of the RF coupling in their lenses.
highdesertmesa wrote:
My understanding is Leica at least tries to correctly calibrate every new lens to hit infinity at the hard stop on an M body, though, right? And outliers can be adjusted? I just wasn’t sure about these little CV retro wide angles since my CV 21 3.5 has been the only M lens I ever owned that hit infinity quite a bit before the hard stop. Returned it since I heard it was common for that lens.
