p.1 #1 · Looking for the flattest-field lens for Leica M11 - minimal field curvature?
Hi everyone,
I'm trying to find a Leica M-mount lens with the flattest field possible - ideally something where field curvature is virtually non-existent. I'm using a Leica M11, and I want a lens that keeps the plane of focus consistent from center to corners without needing to stop down much.
Kudos for more affordable lens that would also take me 90% of the way there....
I've read that lenses like the Voigtländer 50mm f/2 APO Lanthar and the Leica 35mm APO-Summicron-M ASPH have very flat optics, but I'd love to hear from people who've actually tested them on the M11 (or M10/M240).
My main priorities:
Flat field (no curvature)
Consistent sharpness across the frame
Works well with the M11 sensor
Any firsthand experiences, MTF data comparisons, or alternative recommendations (any focal length considered) would be greatly appreciated!
p.1 #3 · Looking for the flattest-field lens for Leica M11 - minimal field curvature?
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Fred has a listing of his reviews. He often includes the field curvature as part of his reviews. Take a look through them, and see how they fare. Fred may have his recollection of which ones impressed him during his testing, too.
As an example of what you can find about field curvature in Fred's reviews:
p.1 #4 · Looking for the flattest-field lens for Leica M11 - minimal field curvature?
Leica 50mm APO M is pretty good if a normal lens fits the bill. Current 50mm Summilux is good also.
No matter what people say, it's nearly impossible for a wide angle lens to have zero field curvature (uncorrected). It's physics. Even some 35mm lenses have very complex native field curvature - modern cameras can do a decent job of correcting in-camera. Petzval designs and old lenses (Leica or otherwise) often have lots of field curvature.
If you need longer, 90mm APO (Leica or Voigtlander). Generally speaking (not universally), longer lenses have less field curvature but can also have some weird distortions.
Based on some of your comments, the Voigtlander APO lenses (50 and 90 for flattest field) would be lower cost options.
p.1 #5 · Looking for the flattest-field lens for Leica M11 - minimal field curvature?
My feeling is the Voigtlander f/2 APO set: 28, 35, 50, 90 are probably worth checking out and definitely Fred's reviews of these.
Of the Leica lenses I own, probably the 21 SEM (better than the VM 21/3.5) and 90/2 APO, 90/4 Macro. I think the 28 Lux is pretty good. Nothing has really jumped out at me about it with regard to field curvature, but it's probably weaker in the midfield than the VM 28 APO and also has persistent blue/purple fringing, even well stopped down, in the extreme periphery. Other Lux lenses I've found to have wavy field curvature, or at least quite weak midfield performance until stopped down past f/5.6. This includes the 21 Lux and original version 50 Lux ASPH. I have not tried the newer versions, but given they were mild optical refreshes, I would not expect signifiant change in FC performance. Also probably the Voigtlander VM 35/1.7 (now discontinued), but I'd have to revisit it to be sure. ZM 21/2.8 has some field curvature as does the 28 Cron v1.
Some of the recent slow VM releases probably also qualify, such as the 50/3.5. Again, see Fred's reviews.
p.1 #6 · Looking for the flattest-field lens for Leica M11 - minimal field curvature?
The reason I’m focused on this is because I really don’t like the look of lenses where distant objects at the sides or extreme corners come into focus at a different plane than the center. I find that uneven sharpness very distracting and unnatural, even though some people might describe it as “character.”
I’d much rather have a lens that renders evenly and naturally across the frame.
p.1 #7 · Looking for the flattest-field lens for Leica M11 - minimal field curvature?
Unfortunately this characteristic is very common with M-mount lenses, especially wide angles. You're dealing with design tradeoffs where often compactness is given much higher priority than low vignetting (which exacerbates the effect of higher corner sharpness).
But again, this characteristic is often addressed in Fred's reviews, or at the least easily discernible in his sample images. Of course Fred has not reviewed every possible M mount lens option but has done so for most recent releases from Voigtlander.
I would also recommend checking the reviews over at http://phillipreeve.net. The main reviewer, Bastian, is very sensitive to, and does not like, this 'feature' in lenses.
This reminds me that the Thypoch 28/1.4 might be a good candidate, based on Fred's and Bastian's reviews.
p.1 #8 · Looking for the flattest-field lens for Leica M11 - minimal field curvature?
The question as asked, can't be answered. It has to be put into context. What do you want to photograph? Most M lenses will be sharp edge to edge when stopped down. If you want to do copywork, that lens might not be appropriate for general photography and/or portraiture for example. If you are doing street photography then there are many times you do want your background (which includes edges) to fall out of focus. The best way to evaluate lenses for YOUR needs is to buy, borrow or rent lenses until you find what works for you. You know, how we did it prior to the internet. The internet hasn't helped because all you get is "what I have" or "what I own" and not in the context of what works for you.
What will matter most is what focal length you prefer to work in but you'll never go wrong with an APO-Summicron-M 50mm f/2 ASPH or APO-Summicron-M 35mm f/2 ASPH
p.1 #9 · Looking for the flattest-field lens for Leica M11 - minimal field curvature?
The irony is that lenses' field curvature (FC) is widely used to emulate the curvature associated with natural human vision. Google's AI summary has a great breakdown of this phenomenon, and all photographers should be aware of it. No one, let alone esteemed makers like Cooke Optics and Leitz, is out to make unpleasing lenses simply because they want to inject 'character' into the imagery.
They, quite legitimately, want to have strong centers 'project' forwards, while downplaying the outer frames in contrast, resolution and illumination. Yes, heresy, I know, but that is how vision works, and it lies at the center of the debate about sterility in APO lenses.
FC is a valuable (often indispensable) design move, because makers are involved in producing lenses that match their vision of aesthetic images. Interestingly, the more widely loved the lens, the more likely it is to have inimitable curvature. It's a fundamental need for many such rendering styles, as see in the Summilux series. (yes, the CF is little changed from the earlier releases.)
If you want lenses that render evenly across the frame, modern Zeiss and its affiliates like Voigtlander are your friends, for their APOs at least. They are prepared to suffer a degree of astigmatism before they abandon the suppression of FC, as seen in the two Otus ML lenses. The early Leica APOs at 50-75-90mm are flat field at infinity, all are marvelous. The Q3 43 also, and the Elmar/SEM pair, all the APO-Lanthars too, the 28mm too.
