How to Use AF Microadjustment on Your Camera

Published January 21, 2016

The most common questions and complaints I hear almost always have to do with AF accuracy, in one way or another, even if they don’t seem like it at first. “I’m trying to focus on this person’s eyes, but the ears are in focus instead,” or, “This lens is front focusing like crazy,” or, “This fast aperture prime was soft the whole time I used it.” Roger has written some rather lengthy, detailed posts about how phase-detection AF works (phase detection being the kind you use on a dSLR in normal, everyday shooting) so I won’t go into a full explanation here. But the gist of his articles is basically this: phase-detection AF isn’t always that accurate. Here’s some light reading, if you feel so inclined:

How Autofocus Often Works

Why You Can’t Optically Test Your Lens with Autofocus

Autofocus Reality, part 1: Center Point Single Shot Accuracy

That last link is the first in a 4 part series, but right there in that first part is a really good example of what AF microadjustment can do. You can read that if you like technical stuff, but I’m about to summarize it in the next paragraph.

So what is it and why is it necessary?

Lenses and cameras are made to certain specifications, and those specs fall within a narrow range of tolerances. Because of the way phase-detection AF works and how it relies on physical calibration for accuracy, if lens and camera tolerances stack up in one direction or another and things are off by minute amounts, then you might see consistent front or back focusing with that particular lens and camera combination. It’s important to know that this front or back focusing is a combination specific issue. You can take 20 copies of the same lens and test them on one camera body, and you might find that most of them are pretty close to dead on, one or two will probably front focus varying amounts, and one or two more will back focus varying amounts. You could then take those same 20 lenses and test them on a different camera body and get completely different results. This doesn’t mean the lenses or the cameras are broken. They just need adjustment, and this is something you can probably do yourself in camera.

How do I do it?

The procedure for making the necessary adjustments is pretty simple, and it’s the basically same across camera brands. Here’s a list of things you’ll need:

  • Camera
  • Lens or lenses to be adjusted
  • Tripod
  • Focusing target


The target can be something as fancy as a LensAlign, or as simple as a book and a yardstick. All you really need is something with a high contrast, flat face you can stand parallel to the sensor plane, and something next to it that will give you a scale to provide a gauge for the plane of focus.


This is a LensAlign.


This is how you do it on the cheap.


Once you have your target, get your camera set up on a tripod and have it level with your target. If you’re using a LensAlign, there are holes in the front face of the target that line up with red circles on the panel behind. If you’re using the book method, try to get the book and sensor plane as parallel as you can.


Here's a 5D Mark III on my trusty tripod, with the image review zoomed in to check accuracy.


Then line up your camera, initiate AF and take a shot. Make sure you’re using the center focus point for this. Using outer points can create all sorts of problems if the lens you’re calibrating has any field curvature. I like to focus, take a shot, rotate the focus ring, refocus, take another shot, repeat a few times to gauge consistency.


Your test shots will look like this.


Zooming in to the image in camera let’s us see how accurate this lens/camera combination is.


Zoom way in there to really see how accurate focus is.


Look at that! This Canon 135mm f/2L is spot on! But they aren’t always like that. Let’s try another copy.


Another 135, another test shot.


And this one ain't doin' so good.


This copy is front focusing on this camera body. Look at the smaller numbers to see the difference. Should be pretty easy to adjust. First go into the adjustment menu. On Canon it’s called AF Microadjustment. On Nikon, it’s AF Fine Tune. On most other camera systems it’s called microadjustment as well. Nikon just likes to be fancy, I suppose.


This is what it looks like on the Canon 5D Mark III. Your mileage may vary.


You’ll almost always see two options, one for a default setting that affects all lenses universally, and one that’s lens specific. I don’t think I’ve ever used the default setting because every lens will be different.


Don't adjust everything by the same amount OR'll just frustrate yourself.


Setting the actual adjustment will look like this:


The little camera and mountain icons are there for easy reference.


If the lens is front focusing, you move the adjustment to the right, away from the camera. For back focusing you go the other way. To get this lens dialed in, I found I needed an adjustment of +9:


Number 9, number 9, number 9...


Once you’ve set it, make sure the camera shows the adjustment is turned on:


ON is good.


And here’s what it looks like after adjustment:


Looks great, right? Can't you see it?


Oh, right. Maybe this will help.


Now it matches the first lens! And that’s it. Once you’ve set the adjustment, you shouldn’t have to think about it again.

Is there anything else I should be aware of?

Prime lenses are generally the easiest to deal with. When it comes to zooms, you may be a little more limited. Most current Canon cameras that have the AFMA function can now adjust for both ends of the zoom, with a corresponding W and T setting. If an adjustment for each end is not available in your camera, you can either adjust for the end you use the most, or find a compromise you can live with. I’ve seen zooms where one end was fine, and the other was off, or both ends were off different amounts in the same direction, or both ends were off in different directions. There’s often no universal solution, unfortunately.

When it comes to 35mm and 50mm primes, you’ll often find that making an adjustment at shorter focus distances may cause longer distances to be off. It’s not that other lenses aren’t the same in this regard, but for some reason it seems to be more noticeable on these focal lengths. There isn’t really a good solution to this in camera, unfortunately. You’ll want to make your adjustments fit your needs, which may be difficult with some lenses. But if you have the Sigma Art series lenses and the Sigma USB Dock, you can actually adjust for both closer distances and longer distances. The dock and related software allow for four adjustments at four different distances with those Art (A1) series lenses. On Sigma A1 zooms, you can make those four distance adjustments at four different focal lengths, for a total of 16 possible adjustments! It’s time consuming, but if you want everything as spot on as possible, this is really the way to go.

The example above needed a moderate adjustment, +9. Larger adjustments aren’t indicative of something faulty, though. On very rare occasions you may find a lens is beyond adjustment. I once owned a Nikon 20 f/2.8D that was like that. I ended up selling it to someone who had zero issues with it on their camera. If you own a lens that’s beyond adjustment, you can either do what I did, or you may be able to send your lens and camera to the manufacturer to have them adjust it for you, as long as both lens and camera are from the same manufacturer. Just know that adjustment won’t be free.

Is that it?

Yep, that’s pretty much it. If you’ve never experienced front or back focus issues before, you’re either extremely lucky, or you just haven’t noticed it. It’s incredibly common, so it’s good to be aware of it. I’ve had countless discussions that started off with, “Well, none of my lenses have any problems on my camera, so your lens must be broken.” And 95% of the time the lens just needed a little AFMA to get it right in line. Whether you’ve been shooting for one year or 50 years, you will have to deal with this at some point. If you’re ever in doubt about whether you’re having focus problems or resolution problems, switch to live view and try using manual focus or AF (in live view your camera most likely reverts to contrast detection AF, which is much more accurate but slower). If your images get sharper, the lens is most likely front or back focusing on your camera. And now you know how to fix that.

Author: Joey Miller

I’m Joey. I love cameras, especially old film cameras, and I can’t remember the last day I didn’t take a photo. Digital cameras are great, and they keep me employed, but I also still like processing my own film. I’m stuck somewhere in the middle. I shoot every single day, no matter what.

Posted in Equipment
  • l_d_allan

    MagicLantern provides “Auto-Dot-Tune” micro-focus-adjustment. Quick and easy. I’m unclear if Nikon is using a similar approach.

  • Chris Jankowski

    Yes, PDAF to get there fast + CDAF to finish and fine tune (both on the main image sensor) is what the Sony A7RII does. In fact, the final CDAF fine tuning may be conceptually thought of as always on, per shot micro adjustment. There is no danger of hunting really, as this is dealt with algorithmically – by limiting the range. Also, the process can be made faster and more predictable by putting slight bias in the PDAF algorithm to make CDAF to start in the right direction.

  • mosswings

    Fine Tuning values change with distance to subject, converging on a fairly constant value as distance increases. 25x is recommended by Nikon, but good luck finding a consumer-level publication by them stating this.
    Reikan published this on the subject:

    There are a couple of bottom lines here: first, choose the fine tuning value that is appropriate for your intended use. If you will only be using the lens at very short subject distances, calibrate closer to that distance (Example: macros). Second, strive for a good balance between optimal subject distance and Fine Tuning value. As the Fine Tuning magnitude gets larger, the ability of the lens to focus at the other extreme may degrade. If you’re pushing 15s and 20s, check the other end of the focus to see if it still is OK.

  • Thom Hogan

    See HF’s comment about PD information. Once the focus got to within CoC, there’s no discrimination available. Note that the Japanese tend to use CoC’s of 0.033 for full frame, which most of us would tend to regard as way too lax.

    AF Fine Tuning doesn’t make focusing faster. It makes it more accurate to the cumulative tolerances in the system. In a DSLR, those tolerance include lens mount position, mirror positions, AF focus sensor position, and lens motor focusing accuracy, as well as a few others. In a mirrorless system, the first three go away but the last one doesn’t. If the lens didn’t go exactly to where the camera commanded it to (and in the expected time ;~), you don’t have focus, you have something close to focus, which is what AF Fine Tuning is designed to adjust for.

    With Olympus, when you use m4/3 lenses on the camera, the camera does mostly contrast detect focusing with PD assist. However, if you put a 4/3 lens on the camera, it does PD focusing and NO contrast detect assist. The reason for this has to do with the design of the lens motors. You can design a lens motor that’s optimal for PD (very fast jumps to specific spots) or CD (fast continuous movement through the focus range). You generally prioritize one or the other. The older 4/3 cameras and lenses were for DSLRs that only had PD, so those lenses were optimized for PD.

  • mosswings

    Not sure what you’re referring to RE: sensitivity. Correction: sensitivity in Clark’s parlance. When I think of AF sensitivity it’s to the minimum light levels in which it can operate, which is for off-sensor PDAF extremely dim light. Clark is sort of saying that, but mixing in aspects of discrimination.

    Yes, I see the line in Clark’s treatise about the image pairs overlaying each other with OSPDAF systems. That’s what I was referring to as short baseline problems. The physical distance between the images in an off-sensor PDAF system keeps this image overlap from happening which makes it more responsive to small focus displacements. In OSPDAF systems it’s also exacerbated by the lack of a discriminating mask or lens, which is also displayed in Clark’s treatise. You may have seen this in DPR

    Describing the construction and theory behind the D300 AF module, which goes into a lot more detail. The Nikon patent I referred to

    is equally fascinating in another way. This doesn’t have a discriminating mask per se, but it does have optics that have the same effect, and the very high effective apertures that keep the image pairs relatively sharp across the focusing range (high DOF, basically). Note that the DOF, and therefore the sharpness of the image, in OSPDAF systems, may not be as well controlled.

    OSPDAF systems basically look slightly in one direction and slightly in another direction and try to derive a phase signal from this, employing as you point out heavy math and large data arrays to improve the performance.

  • HF

    The sensitivity extends beyond the limits of the AF-sensors in DSLRs, explained and demonstrated here:
    Different to OSPDAF

  • mosswings

    Uhmmm. NO feedback control loop has error information if the error signal has gone to zero. It sounds like you’re talking about the short baseline issues of the OSPDAF system, and perhaps the issues that OSPDAF has with the effective aperture of the AF system. Off-sensor PDAF has both a large baseline and a high effective aperture that keeps the images being correlated relatively sharp and therefore easy to resolve. OSPDAF doesn’t have the first and may or may not have the second depending on how it’s constructed. Nikon patented a rather fascinating programmable-aperture-and-orientation off-sensor PDAF system that looks for all the world like an OSPDAF sensor with microlenses over large groups of pixels that speaks to Thom’s point about there being more arrows in the DSLR quiver. This technique appears to address many of the complaints leveled at both OSPDAF and off-sensor PDAF, but clearly it’s optimized for one thing – AF – and isn’t compatible with an all-in-one approach.

  • HF

    Indeed. As far as I read, OSPDAF has no PD information as soon as the lens is in focus. As the relevant rays from different parts of the lens are within the circle of confusion, the camera can’t immediately react to sudden changes in distance and direction of the subject. The information gathered during previous measurements for acceleration (hard) and velocity is not changed until the subject gets slightly out of focus. Then the OSPDAF is able to get a new estimate. All papers I read on the subject try to deal with information theory (filtering and downsizing to get better data) but not different ways of gathering phase information.

  • Greg

    If the AF is still off, shouldn’t the on-sensor image still be out of phase after focusing if the motor doesn’t go to the correct spot? In that case, there should still be focus chasing, but it would be purely due to the requested adjustment not taking the lens all the way. No contrast detection necessary.

    In this kind of situation, I could see AF Fine Tune making PDAF faster, but I don’t understand why it would make it more accurate.

    Then again, maybe the trick is that Olympus isn’t doing a post-focus check, and is assuming that it went to the right spot. However, in that case wouldn’t the amount of adjustment needed be dependent on how out-of-focus the image was to start?

  • Or you can do the same thing that system does manually — switch between live view/contrast-detect focus and phase-detect, and adjust the fine tuning until they’re the same. Both simpler and more accurate than the slanted-ruler method.

  • Of course the future will be different if everyone makes their cameras like Nikon has with the D500/D5 with an automated system for applying AF fine tune.

  • Joey Miller

    Ahh, thanks for the clarification. And thanks for all the other helpful insight in these comments!

  • Thom Hogan

    I don’t think that at all. The geometries of off sensor PD and on sensor PD are quite different. Moreover, it seems that everyone is assuming that the off sensor folk don’t have anything up their sleeve. They do, and as we’ve just seen, the D5 and D500 have automatic AF Fine Tuning. That’s not the only thing they can do, FWIW.

    I suspect that long term the performance cameras will have both on and off sensor PD. You can get better discrimination, especially with long lenses at longer distances, with off sensor PD. With on sensor PD you can get additional information about what’s happening during the shot (and during the blackout of the other system).

  • Thom Hogan

    No, he’s not right about DSLRs versus mirrorless. Phase detect done at its fastest means that the lens motor has to end exactly where the camera told it to go. It’s not just about mirror alignment and mount alignment.

    Now some mirrorless cameras perform a contrast detect fine tune after the phase detect to deal with the lens motor tolerance issue. The problem with that is that this slows focus from what it could be using phase detect alone, and can lead to “focus chasing” on moving subjects. Having taken plenty of DSLR and mirrorless images of very fast and complicated movements, I can tell you that the mirrorless systems still have a way to go to equal the best DSLR focus performance. What I see on the Sony’s, in particular, is that they appear to “cheat” a little. In a continuous shot sequence I don’t get every shot perfectly in focus as I expect with my Nikons (or Canon when I shoot it). Instead, I get a lot of images that are “tolerably in focus,” partly due to DOF, but not nailed.

    As I noted above, Olympus has AF Fine Tune in their cameras, partly because there are lenses that you can mount on those cameras that will only do phase detect (e.g. no followup contrast detect).

  • Thom Hogan

    This is an excellent question, but I think you’re not going to like the answer ;~).

    “Back in the day” we weren’t sampling the data as reliably or at as high a level as we are today. Film wasn’t necessarily flat at the film plane, and unless you had a great loupe and good eyes, you wouldn’t see the offsets that we can easily see today. Worse still, the manufacturers didn’t control for the tight tolerances that are needed today. This is particularly true of Nikon: older, pre-digital Nikkor designs seem to not even fall into a bell curve in terms of how they are off in both mount position and lens motor focus placement.

    So, at a minimum, we have legacy issues that the only way to deal with is via some post mortem adjustment. I suppose we could ask the camera makers to do that for us by sending lenses in and having them CHARGE us for that, but I think the way they’ve done this is fine.

    As for EPOI, they almost certainly had higher margins than the NikonUSA subsidiary does today, and fewer dealers and customers to deal with.

  • Thom Hogan

    Yes, and DOF distribution is something I had to work with the LensAlign folk with because it also varies with test distance. When you’re assessing the front/back pairs of numbers, you absolutely need to take this into account. FWIW, I find judging the longitudinal chromatic aberration to be more accurate. The focus plane should have none, forward and backward will have some, especially on primes.

  • Thom Hogan

    This isn’t actually true. What you’re adjusting for when you do AF Fine Tune is a bunch of tolerances, not just one. In a PD-only system, one of those tolerances is the focus motor in the lens. Olympus, for example, has PD-on-sensor AND also provides AF Fine Tune for this reason: the lens might not have gone exactly where the camera told it to.

    Okay, so you COULD do a contrast detect after the phase detect sequence, but that slows down focus systems, and it introduces the potential for “chase” situations (some might call this hunting).

  • Piotr Krochmal

    Hi I tried many home calibration systems, some use monitor as target others DIY calibration setup similar to LensAlign system.

    For me worked setup when target was made from just printed paper with text. Light was from side to got better contrast. I’ve check best sharpness by LV – as most lenses have lateral aberration just look for moment between green and purple. This is my reference point for calibration. Then I look at distance scale turn LV off, AF on and see what happens, change micro-calibration setting and so on. It is much faster than making photos, downloading them putting filter emboss (best to shown OOF areas).
    I’ve got this process after buying sigma 18-35 with sigma dock (pentax version).
    So main problem was how to fast and reliable check when sharp is sharp.
    And as calibration process required about 3 iterations of full
    calibration I have to got setup that not take me whole day.
    How that info help someone.
    Why A4 text paper sheet? AF point size and AF point mark is two different things.
    Having that size target – I have one variable less.

  • Joey Miller

    Some people suggest 25x the focal length of the lens, but shorter works fine as well. In my 135mm setup, I was about 5ft away.

  • Joey Miller

    You’re right about the dSLR qualification. I guess I figured that was a given after I linked the articles at the beginning, but I should’ve made it more explicit.

    And I’m excited about this trend of phase detection on the image sensor itself. The a7R II is one of my favorite cameras right now because it’s doing it right.

  • Chris Jankowski


    Your statement:

    >>>>Because of how phase detection works, there’s just no way for these manufacturers to calibrate….

    should be qualified:

    >>>> Because of how phase detection works in DSLRs and film SLRs, there’s just no way for these manufacturers to calibrate…

    There is absolutely no problem with phase detection autofocus as a method. The problem is that the phase detection sensors in DSLRs are located normally at the bottom of the camera and the light to them has to take a contorted path. The system must perfectly align this path with the path to the sensor, which is difficult as the path includes a movable mirror.

    This whole silly business of AFMA becomes totally unnecessary the moment you place the AF sensors directly on the main image sensor the way e.g. Sony does it in A7RII. They have nearly 400 PDAF sensors on the main image sensor. This solves several other problems as well e.g. the restriction to the size of the image covered by AF. They cover 80% of the image sensor with PDAF sensors. It is also much simpler and cheaper to manufacture.

  • Chris Jankowski

    Hear, hear,

    This whole silly business of AFMA becomes totally
    unnecessary the moment you place the AF sensors directly on the main
    image sensor the way e.g. Sony
    does it in A7RII. They have nearly 400 AF sensors on the main image
    sensor. This solves several other problems e.g. the restriction to the
    size of the image covered by AF. They cover 80%.

    I am too hoping that the in a few years all cameras will have PDAF and CDAF directly on the sensor.

  • kimH

    Is there a rule-of-thumb regarding distance to target?

  • Joey Miller

    The more difficult things to adjust on my old Mamiya are the lens cams. Having to adjust all 6 lenses I have for that Universal body in conjunction with the rangefinder is the most tedious thing I’ve ever had to do. God forbid the body or any of the lenses take a big bump and I have to do it all over again. One of my 100mm f/2.8s is so off now that I only use it with the ground glass.

    But I think the prominence of the need to correct focus has more to do with how exacting digital is compared to the old film days. Most of us back then didn’t bother zooming in at 200% and pixel peeping our images to death. Now that we can do that, the flaws in phase-detect AF are more apparent, and AFMA is really the only way to deal with that on a large scale. Unless you think manufacturers should start selling cameras and lenses with a coupon for free calibration. I don’t think that’ll fly, though, without big price hikes to cover the extra work. Any piece of sophisticated machinery is going to need adjustment for perfect use. I personally would rather be able to do it myself than have to pay someone else to do it.

    And people do expect cameras to arrive pre-calibrated and work perfectly right out of the box. I field questions about that very thing all the time. “All my lenses work just fine on my camera, but yours doesn’t, so it’s broken.” And the vast majority of the time it just needed AFMA. The idea that things work correctly as-is without adjustment is the common misconception.

  • J.L. Williams

    Yeah, I’ve adjusted more than a few rangefinders myself (Nikons are easier than most; the original Mamiya 6 is one of the easiest) but what surprises me is that people now no longer expect new cameras to arrive pre-calibrated, but accept it as their responsibility and applaud manufacturers for giving us a menu to do it: “It’s not a bug, it’s a feature!”

  • I think this will be one of the big factors that settles the DSLR vs. mirrorless debate once hybrid on-sensor PDAF+CDAF technology has had a couple more product generations to mature. With rising resolutions, the AF inaccuracies of off-sensor DSLR PDAF are getting more and more visible.

  • Joey Miller

    Good point! Thanks for the extra info.

  • Joey Miller

    Well, on a rangefinder the adjustment is mechanical. I’ve done rangefinder adjustment on my old Mamiya Universal, and it’s not fun, nor would I expect the average user to be able to do it. And you don’t have to calibrate your own gear if you don’t want to. You can always send your camera and lenses back to the manufacturer and have them adjust everything for you, for a price. Because of how phase detection works, there’s just no way for these manufacturers to calibrate every copy of a lens to every copy of a camera in their inventory. It’s a combo specific issue. As far as I know, this has always been the case. We just haven’t had a way to adjust it ourselves until recent years. I guess it’s just in how you view it. It’s either the manufacturers being lazy and making you do it yourself, or it’s them allowing you to make minor adjustments when necessary and skip the expense of having it done professionally. I prefer to think of it as the latter.

  • Clint Cheng

    It should be noted that depth of field distribution is not always 50/50; it varies with focal length of the lens begin tested.

    For example:

    Focal Length : Rear : Front
    10mm : 70.2% : 29.8 %
    20mm : 60.1% : 39.9 %
    50mm : 54.0% : 46.0 %
    100mm : 52.0% : 48.0 %
    200mm : 51.0% : 49.0 %
    400mm : 50.5% : 49.5 %

  • J.L. Williams

    Great explanation, but I can’t help wondering when lens calibration became the consumer’s job rather than the manufacturer’s. “Back in the day,” if your 50mm f/1.1 Nikkor wasn’t focusing your model’s heavily-mascared eyelashes accurately on your Nikon SP, you sent them (the camera and lens, not the eyelashes) back to EPOI and they’d fix it.

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