How to check how decentered your lens is

How to check if your lens is decentered?

check lens decentering centered centering well bad sample variation

You may have already heard of sample variation or decentered lenses. In this article we will show you how to easily test your lenses for proper centering. If you know how it works it will take you less than 5 minutes per lens!

Where this test originates from

This test was published by the German Gletscherbruch homepage, but as this website is only available in German we decided to write an English version.

How does it work?

What you will need:

  • Tripod
  • Some building far away (chimney, antenna, church tower etc.)

How to set your camera:

  • use the widest aperture of your lens (some lenses have very bad corner performance, stop these down until there is visible detail in the corners).
  • manual focus
  • manual exposure (or use AEL toggle)
  • IBIS/OSS off
  • electronic first curtain shutter off (if you have a stable tripod)

What to do:

  1. You set up your camera on the tripod.
  2. You put your target in the center of the frame and you focus on it.

    Focus is on the chimney in the center of the frame
  3. Do not change focus!
  4. Move your camera on the ballhead until your target is in one of the extreme corners of the frame and take the shot

    Chimney in upper left corner
  5. Repeat step 4 for the other 3 corners.
    Chimney in upper right corner
    Chimney in lower left corner

    Chimney in lower right corner

How to rate your shots:

Before you rate your shots there are a few things to consider:

  • A perfectly centered lens does not exist and a very slight decentering you will only rarely if ever notice in your pictures.
  • There is no objective standard. You will have to decide if what you see is an issue for you or not and if you can expect to find a better copy.
  • Every manufacturer ships decentered lenses, but some are worse than others. Zeiss for example has significantly better quality control than Sony, but no manufacturer is perfect.
  • Usually fast and wide lenses are more prone to decentering.
  • Zooms are more prone to decentering, compared to primes you should lower your standard a bit.
  • When testing zooms for decentering you should do it at the extremes and in the middle.
  • If your lens has field curvature the corners will look worse than the center. To check centering you need to compare the corners to each other, not compare the corners to the center.

The “perfect” lens

check lens decentering centered centering well bad sample variation

This is pretty much as good as it gets, there is almost no variation. You just won the lottery.

The “almost perfect” lens

check lens decentering centered centering well bad sample variation

One corner is very slightly worse, but this will be pretty much unnoticeable. This is a perfectly usable lens.

The decentered lens

check lens decentering centered centering well bad sample variation

This one is badly decentered in a way that it might actually have a visible influence on your results. You might want to consider returning this or have it serviced.

We can also highly recommend Roger Cicala’s article on optical quality assurance. It is a more complicated business than you might have guessed.

Further Reading

The following two tabs change content below.
My name is Bastian and I am your expert here when it comes to ultra wide angle lenses, super fast portrait lenses (ranging from a 50mm f/0.95 to a 200mm f/1.8) and I also have reviewed way too many 35mm lenses. Don't ask me anything about macro or wildlife shooting though.

Latest posts by BastianK (see all)

105 thoughts on “How to check how decentered your lens is”

  1. Hi Bastian
    Thanks for this (as usual) usefull article.
    I have one silly question : how to easily put the four 100 % crop next to each other for better comparison ?
    Thanks again and I look forward to your next post.

  2. Hi, for me, it is not clear, why one set of pictures is better than the other, since it is not mentioned, what your should be looking out for.

    Could you please update the article to make this more clear.

    Thanks a lot, also for all the other great articles!

  3. Where would I service such decentered lens when it’s out of warranty (used, vintage, second hand)? And can or do the usual manufacturers repair such decentering? And round about what costs are we talking about?

    I’m thinking that it’s quite difficult to find some one who can fix decentering on a vintage lens. And one modern lenses, it might be too difficult or expensive and the service just rejects the case (all within acceptance). But I never tried …

    1. Depending on where you live, there should be choice of “old school” repairpersons you can send your lens to.

      Before camera lenses started being considered “disposable” electronic items (!!), it was common practice to have lenses Cleaned, Lubricated and Adjusted (CLA’d) every few years (or decades), especially if a working pro.

      1. Yes, I know. But decentering is another level, isn’t it? Most 1st party manufacturers refuse to touch a decentered lens and send you right away a replacement. Micro-aligning such modern, complex lens designs is very, very difficult or even possible.

        1. Yes, not all lenses can actually be aligned.
          Yet not every optical design is prone to decentering in the same way.
          With more thick elements it is less of an issue compared to a few thin ones.

  4. Your post is right on time, I got my Zony 35 1.4 yesterday. Have been reading up all the posts on decentered copies of that lens at Fred Miranda and now I am a bit scared to do that test …

  5. Thanks for this very useful article. Have heard about it but didn’t know much on how to test it. I’ll now get down to test all my lenses.

    Many thanks

  6. Very useful article especially with the example images. However, the first bullet on how to setup the camera is a bit unclear as the parenthetical seems contrary:
    – use the *widest aperture* of your lens (some lenses have very bad corner performance, *stop these down* until there is visible detail in the corners).
    – use the widest aperture of your lens with reasonable corner sharpness (some lenses have very bad corner performance, stop these down until there is visible detail in the corners).
    Also, a sentence under the decentered lens pointing out the differences in sharpness would probably help clarify things for people new to decentered lens testing.

  7. Hi this is Lee

    last sunday

    I had tested my batis 18 mm with your test mehtod but i can not tell mine is good or not.

    could you check my result??

    if you can please send me a mail than i will reply to you with my shots

    thanks for your tip.

  8. Okay it seems i got unlucky with all my lenses 🙁
    I have the 24-105mm F4, 16-35mm F4 and the 55mm 1.8

    Could you guys tell me if i should give them back?
    I didn’t notice any of that during my everyday use.

    It would really be appreciated!

  9. Good article, pretty easy to follow. Received a copy of the FE 85/1,8 today and did one test on an infinity object (mast) and one on a closer one:!AlCoUQ0jvInBgYp-nNmK_9arjrQnCA

    To me the bottom corners look slightly worse than the top ones but it is slight. I’m pretty happy one side or corner is a smear but then this lens has been described as ‘sharp into the corners wide open’ so I wonder what others think?

  10. Thanks for this interesting paper. In your experience, did you see badly ‘decentered’ lenses that were actually fine, but the ‘decentering’ effect was due to a bad adapter with non-parallel mount planes?

      1. Oh, I know, you are right! I forgot to mention, but I did a test based on your post too. The result was soo bad on the left side that I was sure I must did something wrong. Here it is:
        (just bottom left and bottom right corners)

        The guy who selling this lens did some test shots too (he mentioned me this blog actually, for which I was very grateful) at f4 or 5.6 and it was pretty good. Could this be true that a lens show almost nothing at all at f4 and on its widest f2 it is so bad?

        1. I don’t think you did anything wrong, this sample of the lens just sucks.
          Decentering goes away when you stop down enough.
          I would not buy that lens though, especially if you intend to use it for e.g. astrophotography.

          1. Thank you very much for your help! The seller is a very kind man, he is willing to take the lens back after these tests.
            I am just wondering now, if I should try out more samyang(rokinon) 12mm f2 or the samyang 21mm f1.4 could be a better lens? (I saw too many decentered samyang 12mm f2.) With fuji x I don’t have many choices for astro.

          2. There isn’t really much choice, try another Samyang 2/12 or have a look at Laowa 9mm 2.8 instead.
            With the 21mm you will be doing panorama for milky way all the time, not sure whether that fits your workflow.

  11. Hi! Thank you very much for this helpful article. I am also one of those having a hard time judging my results. These are some samples from my new Tamron 15-30 G2 on a Nikon D850. I am not so convinced, one corner seems to be visibly sharper than the others, even at f/8. But what do you think?
    Thank you!

    At 15 mm, f/2.8:

    At 15mm, f/8:

    At 30mm, f/2.8:

    At 30mm, f/7.1:

    1. Very often when a lens is decentered that means the field is tilted and the bad parts look better when focus is adjusted.
      I cannot tell you whether you are happy with this lens or not, but as you decided to make a post that probably means you are not happy so you should return it I think.

  12. Hi! Maybe I’m a little bit stupid.. but I don’t really understand how I should take the four photos… I don’t have a good tripod and no ballhead, is it possible to do this handheld? Don’t you change the focus if you move the camera while handheld? For even more clarity in the description it would be great if you add photos of the camera positions while taking the four photos.
    Kind regards,

  13. Hi Bastian,

    I just got my copy of Sigma FE 35 f/1,2. While I’m very happy with its performance and the images I get (people), the de-centering test seems to show that I might have a problem. This wouldn’t be a huge deal were this lens cheaper, but at this price I think it should be less obvious.
    Stopped down everything is fine across the frame, from let’s say f/6,3.
    Could you asses please? The upper right corner is the one troubling me.

    Thank you!

  14. Nice and easy and short. Thanks Bastiak, I had read so many times but not occurred to do it with a tripod only a flat target

  15. Great article as usual, Bastian. I am a bit confused by step 2 to 4. Why focusing on a subject in the center of the frame first, then moving it to the corner positions, instead of putting the subject in the corner positions directly, then focusing on it?



    1. It is possible, that an element is very slightly tilted, so one corner is best focused slightly in front of the center and the opposite corner is best focused slightly behind the center.
      It is further possible, that this very slight tilt may still be in your tolerances, but if you focus on the corner the deviation between those corners will be double compared to what you get when you focused on the center before.
      I hope I could make this somewhat clear.
      For a perfectly centered lens it should indeed not make a difference.

      1. Hi Bastian. If you focus on the center and one corner is tilted forward while the other is tilted backward by the same amount, the two corners will look equally out-of-focus, and you will wrongly conclude the lens is perfectly “centered” (untilted)

        The doubled difference you mention instead always correctly shows you how tilted the lens is.

        Fred at FM also promotes center focus in his method, and both your page and his are referenced frequently, so I thought I would send you this note for consideration.

        Cheers, Richard.

        1. In case it wasn’t clear in my comment above, I thought I better add that what I am proposing therefore is that focusing on one of the corners rather than the center is preferable because it is both more reliable and more sensitive.

          1. You will have a hard time finding a perfectly centered lens, they all show some degree of tilt.
            When you focus on the corners you will end up returning many lenses that are indeed perfectly usable for any task.
            This is not about finding the perfect lens that doesn’t exist, this is about sorting out the real duds.
            Therefore focus on center is preferable for 99% of people.

            As you already know about these things you are probably also not the target audience of this article.

  16. “This is pretty much as good as it gets, there is almost no variation. You just won the lottery.”

    In the first example, I wouldn’t necessarily conclude that four simultaneously sharp corners means you got the best possible sample. It’s still possible that the maximum centre MTF wasn’t necessarily achieved. One could conclude they received a sample that exhibited even behaviour across the field and possibly a relatively flat field.

  17. Hi,
    Thanks for posting such a helpful article.
    I have a lens Pentax FA 24-90mm which for sure is decentered at 24mm. But starting from 28mm the decentering effect becomes negligible and totally dissapears between 35 and 90mm.

    I wonder how this is possible. If decentering effect is visble at one FL, should it not be visible at all other FLs?

    Can you explain such phenomenom?


  18. Hi Bastian. I bought a used M-mount CV 35mm 1.7 to adapt to my A7 and the top two corners are much softer than the bottom two. The top left corner is very bad, much worse than all the rest. The bottom right corner is decent. Here’s the test:

    I know this lens has a focus shift problem in the corners due to the Sony sensor, would the problem show like this? I thought each corner would be more equally affected. Please reply if you can, I’m trying to determine if this lens is defective.

    Unfortunately I won’t be getting a correction filter for some time, Opto-sigma seems to have a delay for now due to the virus.

  19. Hi Bastian,

    Thanks a lot for posting this very usefull article !!!
    Could you have a look on these lenses (shooted at 42Mp)?

    I am not sure about my analysis :
    The 85mm seems decentered. The 55mm also but little less.
    The 15mm & the 24mm seems not so bad (even if a little something on the 24mm)

  20. Hi everyone. I am testing a couple of lenses at moment using your method. Is the way you do it at a distance in corners the same regardless of focal length? Will it test decentering of a macro lens as well as a standard 50mm lens using same method? Is this a way of standard testing to see if any problems? Thanks dean

    1. If you want to use your macro lens mainly for taking pictures of stamps or something like that it may not be the best method, otherwise it works for every focal length.

  21. Hello everyone. Thank you very much for this article.

    I got a Tamron 28-75mm F2.8 Di III RXD this week and I am trying to decide if I should keep it or not. I am really worried about decentering. I have never done this test and I don’t know if I am doing it properly. I followed your instructions on a Sony A7ii. I tried from 24mm, 35mm, 50mm and 75mm.
    Could you have a look, please? Am I doing something wrong?

    Thank you

  22. A question: if I have a tilted bayonet/tilted sensor, will I have similar poor performing corners on each lens/focal length? Or would it be more prominent with a particular lens? I have had three copies of a “bad” 24mm lenses and want to rule out sensor/bayonet tilt but I can only see noticeable differences on those 24mm lens, not at 35mm, 50mm, or even 14mm…

    1. The faster and wider your lens the more pronounced it shoud be.
      Lenses like 24mm 1.4, 20mm 1.8, 15mm 2.0 or 35mm 1.2 will most likely show issues whereas with longer/slower lenses a tilted bayonet or sensor will be harder to detect.

      1. Makes sense to me and confirms to me that I coincidentally had three “bad” lenses. Corner-to-corner differences were obvious at 24mm 1.4 on each copy and nearly no distinguishable difference corner to corner at 35mm 1.4. Thanks for your help!

    1. Is there a standard for what magnification the crops should be viewed for comparison (100%, 200%). It seems with greater magnification decentering seems more of an issue.

Leave a Reply

Your email address will not be published. Required fields are marked *