Lenses and Optics

There Is No Free Lunch, Episode 763: Lens Adapters

Published September 26, 2013

Lens adapters can be useful things sometimes, letting you mount one brand of lens on another brand of camera.

One thing that has always bothered me, though, is the idea of doubling the number of lens-mount interfaces. When you look at the thick metal pieces on the front of the camera and the back of the lens, and then consider that they have to be lined up exactly parallel to the image sensor, it’s kind of amazing it works.

Although it doesn’t always work. Lloyd Chambers first reported years ago that with high-quality, wide-angle lenses you could detect very small misalignments in the camera-lens mount. Misalignment of 10 microns from side-to-side was enough to cause blur on the sides of the image. Since then a lot of other people have confirmed the same thing.

So when I hear people cavalierly talking about putting an adapter on their camera I tend to cringe. When a single camera-lens interface has enough variability to sometimes be visible, adding another large piece of metal with another mount interface seems a recipe for problems.

Don’t get me wrong. Generally, they’re acceptable or people wouldn’t use them. But I always am curious about what acceptable looks like in the lab.

Optical Bench Testing

We’ve been working a lot with our optical bench, testing large enough quantities of each lens to develop our acceptable ranges, since we plan to start adding this testing to the Imatest testing we currently use for quality assurance. An optical bench isn’t necessarily better than image-based testing programs like Imatest, but it has some specific advantages.

One big difference is that an optical bench tests at infinity (on wide-angle lenses, Imatest or DxOAnalytics may be testing at 4-6 feet focusing distance). Another is it tests the lens directly; the variability of a camera body is eliminated from the loop. There are some things a bench doesn’t do as well, too. For example you don’t get a full picture of the entire lens in one run; you get a line of data from one side to the other. You have to rotate the lens in its mount and do several lines to get a complete picture of the entire lens surface.

Since the information from our optical bench is different from the Imatest graphs I usually use for illustrations, let me go over one quickly.


Wells Optical Bench printout of MTF by field of view and frequency.


The horizontal axis shows degrees off-center, with “0” the center of the lens. The vertical axis is the MTF reading (“1” being theoretical perfection and “0” being gray mush).

The charted colors show various frequencies. For this graph we chose to show the MTF at 10, 20, 50, and 80 line pairs per mm. Most manufacturers’ MTF graphs limit themselves to 10 and 30 or 10, 20, and 40 as frequencies. We’re including some higher frequencies just because we’re still learning about using this tool to identify bad lenses.

There are two charted lines at each frequency, one representing tangential and the other sagittal lines. When the two lines of the same color are separated, there is some astigmatism. (You don’t have to worry about the terms – just that if the two lines of the same color are widely separated, that’s not good, close together is good.)

The graph above is of a good copy of a good lens, the Zeiss 35mm f/2.0. There are some slight differences away from center with one side having a bit more astigmatism and the other a bit lower MTF at higher frequencies, but this is really minor stuff that wouldn’t show up in photograph.

To give you a bit more experience with this kind of graph, below are printouts from 4 other Zeiss 35mm f/2.0 lenses – all of which are optically excellent as determined by Imatest and careful pixel-peeping.



Again, let me emphasize that what you’re seeing is normal (actually less than normal) copy-to-copy variation in good copies of the lens. Actual bench testing is almost like fingerprinting. No two copies are exactly the same. Notice the similarities. There is nearly no astigmatism right at the center and similar MTF values, particularly at the 10 and 20 /mm frequencies that are most critical.

To give you some idea of what a not-so-good lens looks like on the same set of parameters, here’s one that’s not so good.

Notice this one is still quite good in the center, but has some major problems developing on the right side. The settings on the optical bench we used for this series make it look much worse than it really is. While the graph makes it look like the MTF drops to zero, that’s simply because the settings we’re using report zero if focusing distance changes greatly or vignetting become severe.  That makes a nice warning signal for ‘some human needs to come check this lens’.

Our parameters are pretty tight: the awful looking graph above actually is a lens that looks a little softer on the right side, but certainly not horrible. An online sized jpg would look perfectly fine, at 50% pixel-peeping or in a large print you’d notice it. I’ll go into more detail about what we can do with the optical bench in some later posts; I just wanted to give you a quick overview for now.

Using Adapters on the Optical Bench

One thing you probably haven’t thought about is that lenses have to be mounted on the bench in order to do these tests. That requires a separate, fairly expensive mount for each brand of lens. Obviously we had to pony up to get mounts for Canon, Nikon, NEX, and Micro 4/3 lenses. But, since I was already pretty unpopular in the accounting department, I hoped to avoid spending a few thousand more dollars to buy Leica, PL, and other mounts for lenses that we have a lower number of copies of.

I knew adapters might cause a problem, but thought, since we carry so many copies of various high-quality adapters, I could certainly find a few that were accurate enough to use. Once again, Roger’s assumptions were way off base. I won’t bore you with dozens and dozens of test results. But I’ll show you a good example. In this case, we took the lens in the upper right of the 4 examples at the top of the page and tested it on a number of Nikon to NEX adapters. Here are 6 examples.

I won’t bore you with another 20 graphs that look pretty much like these. We tried Leica to NEX and Leica to Micro 4/3 adapters, Canon to NEX, etc. We tried different lenses on one adapter. It didn’t really matter. None of them would be acceptable for testing. Not one.

I’ll point out that we carry only name-brand, fairly expensive adapters, not eBay $29 adapters. All of them are tested frequently and used frequently and none of the ones I tested today had any problems. Still, not one of them would be acceptable for testing, so I guess I’m going to have to order those expensive lens mounts after all.

What Does It Mean in the Real World?

Like a lot of laboratory testing, probably not a lot. Adapters couldn’t all stink or people wouldn’t use them. Like a lot of tests, you can detect a very real difference in the lab that doesn’t make much difference at all in the real world.

Videographers are the primary users of adapters, and probably won’t notice the problems at all. Video and cinema cameras shoot at lower resolution (even 4K video) than photography and tend to concentrate on center-frame so they’re unlikely to see a problem.

Even photographers who use adapters are often adapting a larger format lens to a smaller format camera (Leica full-frame lens to Micro 4/3 or APS-C camera, for example). Assuming the lens is higher quality than a native lens they would otherwise be shooting, they might be perfectly happy. Still, I should point out that I  only tested these 35mm lenses out to +/- 12 degrees (their field of view is actually +/- 30 degrees). Even on a Micro 4/3 camera, the lens would have a field of view of +/- 15 degrees what we see here at 12 degrees should be noticeable.

In the examples above, though, center resolution is pretty much unchanged, it’s only when you get away from center that you start to see issues. So someone shooting portraits and centered subjects is unlikely to notice an issue. A landscape photographer, though, would likely see some problems along the edges of the image.

Putting a great lens on your camera via an adapter might still be better than an average native-mount lens. On the other hand, that great lens certainly wouldn’t be as good as it would be on its native-mount camera.


Roger Cicala


September, 2013

Author: Roger Cicala

I’m Roger and I am the founder of Lensrentals.com. Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

Posted in Lenses and Optics
  • Timur Born

    I am mostly just curious anyway, as I don’t own any glass that would go on any adapter. Albeit it’s still interesting to know how much of an option the “native” adapters are for those interested in the E-M1 and A7(r). My E-M5 has to go due to limitations with AF-C (kids) and ergonomics (controls and size). So apart from pondering if a 6D/D600 might be the better choice the E-M1 is a strong contender. And since the adapter comes free it opens the possibilities of making up for the smaller sensor with something like a 12-35/f2.0 FT lens.

    Albeit the A7(r) doesn’t seem too interesting from an ergonomic point of view I like the combination of FF sensor + fully embraced mirrorless concepts (EVF + screen + on sensor AF + live preview) over traditional mirror concepts. But with a truly lacking lens line-up you are kind of forced to use an adapter to even begin using it.

  • Dan

    What is your opinion of using an Olympus 100mm f2.8 OM lens and 28mm f3.5 OM lens via adapter on a Canon 6D? The focussing method would be using Canon’s manual focus Eg-S screen. Is there a quality adapter for this example? Many thanks.

  • Roger Cicala

    Sem, the test we run goes through the full focus possibilities of the lens automatically. Focus is not an issue.
    Focus adjustment has to do with autofocus – and these are lenses tested on a bench. No camera involved at all.

  • Sem Svizec

    Did you doublecheck with introducing controlled short amounts of positive/negative extension, and what focus adjustment can do about this? I mean, if the inf setting is not accurate (known to happen also with come lenses straight out of the factory), in practice one would usually adjusts focus.
    And how about a reality check with a tilt adapter, or a TS lens?

  • Roger Cicala

    I saw Ming’s article and I agree with him. I’ve already heard dozens of people who can’t wait to adapt their Leica glass to A7Rs. Will it be better than Sony’s first lenses? Almost certainly. Will they be as good as they are on a native mount Leica camera? Almost certainly not.

    I’m glad I agree with Ming (because I wouldn’t dare argue with him) – adapters are useful tools, but there’s a bit of trade off.

  • Timur Born

    Thanks Roger. I am asking because of a recent Sony A7 related article on Ming Thein’s site that mentions: “Don’t think you can get away with adaptors: the planarity of such adaptors is going to be absolutely critical, especially with such short flange distances and resolution numbers. You’ll actually be able to see the effects of a cheap, out-of-plane adaptor – it looks a little like a tilt. (I know this because I tried Hasselblad lenses on my D800E; none of the three adaptors I obtained had sufficiently tight tolerances to avoid this problem.)”

    And I also know at least one DPR user who regularly shims his native MFT primes on MFT bodies. 😉

  • Roger Cicala


    I didn’t test original equipment adapters. But since we already know that camera to lens mount is a source of variation for every manufacturer, I’d be surprised if they can make an adapter without it. Better than third party? Perhaps somewhat.

    Remember, though, the point of this article is mostly for people doing tests/reviews on adapters. The numbers, if they run numbers, will probably be affected. Will it actually affect pictures? Probably not, especially if you’re not shooting at f/1.4 like these tests were done at.


  • Timur Born

    Roger, did you only test cross-platform adapters or did you happen to test original manufacturer adapters, too? I mean something like Sony E to A mount or Olympus FT to MFT. Is there reason to believe (hope) that these original manufacturer adapters are made to tighter specifications (no or less shimming needed)?

  • Andrew Cameron

    Many people use 4/3rds lenses via the MMF-3 with OM-D E-M5 or E-M1 camera bodies.
    I have 7-14mm, 14-35mm, 35-100mm and 90-250mm lenses and have found no problems at all… do you consider the MMF-3 adapter would be “acceptable for testing………”?
    If you did such a test, I’m sure owners of the lenses similar to mine, who now use them via a MMF-3 on E-M5 or E-M1 bodies, would find such a test interesting.
    However, I’m fairly confident that Olympus, knowing how many top grade lenses would be used via the MMF-3, would be very careful with their manufacture and quality control.
    A test, as I said, would make interesting reading.

  • Daniel

    LensRentals has identified a value to lens buyers and renters: testing their lenses before sending them to clients. This really means that manufacturers release lenses that have lower quality than a careful photographer is willing to accept. But I don’t access to an optical bench. Wish there was a dealer who tested lenses before sale. That adapters add problems to lens quality is worth knowing as well. Good job Roger and LR crew!

  • AJ


    Sagittal lines are basically radial (I wonder why they couldn’t have been described as such?) 2 dimensional lines as visualized from the front of the lens.
    Tangential lines are tangents to a circle who’s epicenter is the center of the lens (now that one makes sense!).
    However a lens is 3 dimensional so if one were to view a lens from the side then the correct visualization would be a plane through the lens (or elements as they would appear in a multi-element camera lens). So Sagittal (and tangential) plane makes a lot of sense.
    That’s my explanation and I’m sticking to it until something better comes along 🙂 (said that to my wife whilst we were walking down the aisle. She didn’t seem to be impressed. Bouquets can be put in all sorts of unusual places. The organic parts are fine. It’s the pins and wire they use to keep them arranged that’s problematic).

  • AJ

    Roger, surely you jest?
    People would do this?
    (Wears look of horror …)

    Roger Cicala said:

    Dave, I wouldn’t want or expect people to stop using adapters any more than they should stop teleconverters or extension tubes. But lens reviewers and testers shouldn’t be testing lenses mounted to adapters and considering the results valid for what the lens would do in native mount.

  • Kerry

    I know that tilt-shift lenses work great, for example the Canon 17mm. Most large format cameras provide multiple movements, and these cameras produce superb images.

    I also know that it is very difficult and expansive to make a lens adapter that is precise enough to maintain image quality.

    How can both of these seemingly contradictory conclusions both be true? How can a multiple degree lens tilt work just fine while just a few microns of asymmetry be such a problem?

  • someone

    Hey Roger,

    I haven’t heard back from you regarding the proper definition of sagittal lines as I posted on October 1, 2013 at 4:10 PM.

    Thanks for your attention! 🙂

  • Roger Cicala

    Tim, we haven’t yet. I’ll try to get around to that in the next few weeks.

  • Tim K

    I am curious if you tried adapters and lenses manufactured by the original company, ie sony adaptor for A mount to E mount. Does the original manufacturer suffer the same IQ impact as an after market company or is there specific system or manufacturing related knowledge that can advantage these devices?

  • All of my lenses are adapted alt lenses. I use Leitax adapters which are basically permanent mount conversions. They are rock-solid and machining quality is top-notch. Never had a problem.

  • Tord S Eriksson


    I use a few F Mount lenses on my Nikon V1, using the FT1 adapter, and there are much fewer problems when using long lenses than wide ones, like the 70-300 VR acts like it is native to the V1, while 35/1.8G DX didn’t work quite as well.

    When it comes to the NEX range, the native lenses are more, or less, useless (there are a few exceptions, of course, like the Sony-made Zeiss 1.8/24), so any adapter combined with Full Format tele lenses work surprisingly well. I’ve tried both Nikon and Pentax, no major issues!

  • John H.

    I actually don’t think I’ve ever seen the term “cavalierly” before this post.

  • Spanky

    “Putting a great lens on your camera via an adapter might still be better than an average native-mount lens. On the other hand, that great lens certainly wouldn’t be as good as it would be on its native-mount camera.”

    A perfect summary.

  • For those saying smaller sensors will show less issues: no, they won’t, if you keep field of view and depth of field constant.
    You have to compare FF 50mm f/2.8 ISO 200 with m43 25mm f/1.4 ISO 800, as those are the options that will give you equivalent field of view, depth of field, and exposure.
    If you’re comparing 50mm f/2.8 on FF and on m43, of course the m43 has an advantage. But when you switch to a wider lens (25mm) and thinner DoF (f/1.4), problems will be more pronounced, this will compensate for the smaller corner-to-corner distance in the sensor, and you’ll be back at square one.

  • Well I just bought a Metabones Leica M to Fuji X adapter for my Elmar 135 I have in the mail. I might have bought a cheap one but this article convinced me a high grade item would be a good idea.

  • someone

    Regarding the link to opticampus.com about sagittal lines, I believe the drawings are incorrect; specifically, they’re swapped (?). From all I’ve read sagittal lines run from the center of the lens outwards (like spokes on a wheel). The image you referenced mentions the sagittal “plane,” rather than a sagittal line; so I don’t know if that’s the difference there (?). Example: http://www.cambridgeincolour.com/tutorials/lens-quality-mtf-resolution.htm

  • I’d like to know a bit more detail on this testing. Something seems to be odd here. For instance on the diglloyd blog (you cited) he seems to find its less of an issue with lenses longer than 50mm and on sensors smaller than full frame. This (what he says) makes more sence as with a shorter focal length lens a smaller movement (extension) is needed to make a larger difference in focus distances. So if using a 24mm lens on an adapted mount one would expect tolerance differences more significant than with a 50mm or even a 300mm. Quoting from diglloyd:
    “Why short focal lengths? Because the percentage error for any fixed alignment error is much larger. My experience has been that 50mm on up is the safe zone, with 35mm on down becoming more and more sensitive to alignment errors (that’s on full-frame DSLRs).”

    “And the evidence in reviewing the Olympus E-P1 and Panasonic G-1 suggests to me that the four-thirds and micro-4/3 format is much less prone to misalignment.”

    which seems to be different to your findings.

  • My free lunch tastes great! But it’s actually not free. My adapters cost between $12 and $25 (USD). And unless you camera is a SOLID titanium body (which none are) it warps and twists with the weather and lens weight more than what this article discusses. He said it best himself when he said: there’s no real-world meaning to these tests. 😉

    Kind of an amusing read though.

  • zosX

    To the person that asked about adaptalls. I have used two adaptall lenses quite a bit with my Pentax cameras in the past. They were just as sharp as normal lenses with regular K-mount. The 28mm had some CA and coma towards the edge of the frame, but I’m pretty sure that was a fault of the lens and not the adaptall adapter. The adapter I have is well built. If you ask me, with the sony NEX there is something else going on IMO with the edges. Using lenses that are designed for similar flange distances to what you are adapting too shouldn’t cause any real problems with a good adapter IMO.

  • Roger Cicala

    Dave, I wouldn’t want or expect people to stop using adapters any more than they should stop teleconverters or extension tubes. But lens reviewers and testers shouldn’t be testing lenses mounted to adapters and considering the results valid for what the lens would do in native mount.

  • Roger Cicala

    Andrew, we could change things by rotating – moving the tilt around. But we’d need to do cuts every 30 degrees for 180 degrees to find an on-axis point and we weren’t spending that much time. Our protocol at this point is to test at zero and 90 degrees – remember our original point wasn’t to make a study of adapters, but simply to find an adapter accurate enough to avoid buying more $1,000 lens mount discs.

  • Andrew Z

    This seems much worse than expected. Surely all the adapter can do is tilt the lens off axis in which case if you rotate the lens enough you should still be able to get a good reading for one line (ie it will show improvement as you approach the line). Did that happen? If not there is another factor at play.

  • It’d be nice if you could have some data that compares native mounted lenses with adapter-mounted lenses — and stop with the treating it as zero stuff (what’s the point of that?). Also, are you actually testing every degree FOV or every 4 degrees? Why not test every integer? Anyway, this data is not really useable at the moment. If you could show us which brands were most accurate and precise over several instances of each brand (5 of each, say), that would be something we could use. Because I don’t think people are going to stop using adapters..

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