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

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My name is Bastian and for many years I have been mostly shooting Nikon DSLRs. As of today I have made my transition from Nikon to Sony and I am mainly using small but capable manual lenses. My passion is landscape photography but I also like to delve into other subjects from time to time.

Latest posts by BastianK (see all)

45 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.
    Adrien

  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).
    Perhaps:
    – 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.
    Best

  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

    https://postimg.cc/gallery/15fjsr8c2/

    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!
    thanks
    Ansgar

  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:
    https://1drv.ms/f/s!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: https://drive.google.com/open?id=1XbNuMHakji-5QoKrZ-UTLttjE6nYECbu
        (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.

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