Automatic AF Microadjust Calibration Software now available!

by planetMitch17 Comments

If you've ever tried to use the Microadjustment functions on your Canon EOS 5D Mark II, you'll be interested in this story (tho don't yet get too excited if you're a mac user as this is windows only I'm afraid).


Automatic AF Microadjust Calibration Software

Over the past few months, I have spent some time developing an algorithm to perform automatic AF microadjust of a camera and lens combination.  After a lot of late nights trying ways of getting working analysis routines and repeatable data, I have finally got to  a point where I would like to release this software.  At the moment, it has been extensively tested to work with a Canon 5Dmk2, and has been proven to work with a Canon 1Dsmk3, but I will continue to develop it against a 7D and test with the xxD range.  It’s also for Windows only (not a Mac as I don’t have one to develop on).  Oh, and it’s free.

What does it do?

Have you heard of back-focus or front-focus?  Well, Auto Focus Micro-adjust on cameras is meant to allow you to calibrate out any error within the camera’s autofocus system and get all your shots sharp and in focus.

So why do I need software?  Well, you don’t (I’d never make a salesman!)  For a detailed description of how to calibrate a lens, have a look here (it also includes some details about how the AF system works and why you might need to calibrate).

If you decide you do want to calibrate, then the process can be a little fiddly and this software is meant to automate it to get repeatable results quickly.  In my testing, I ran through full calibration of 6 lenses in under 5 minutes.

via Automatic AF Microadjust Calibration Software | Reikan Photography.

(cover photo credit: snap from the video)


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Comments

  1. William Sommerwerck

    As an EE, I remain thoroughly confused about the purpose — indeed, the need — for a microcalibration of the autofocus system. I’ve never heard of microcalibrating the feedback look of an audio amplifier.

    In passive autofocus systems, the focusing system is a feedback loop. A sensor determines whether two slightly different views of the focus point are aligned. If not, the servo motor is run until they are.

    IN THEORY, there should be no need whatever to calibrate the system, micro or otherwise. Yes, lenses vary in the mass their motors have to move, and the friction to be overcome when moved, but I don’t see how these would cause CONSISTENT focusing errors that could be corrected with a close calibration. The system “should” be designed to reduce these errors to nearly zero, especially when one taps the shutter release a second time. *

    I’m also confused by Canon’s warning NOT to use the micro calibration unless you actually have focusing errors in your images. If I recall correctly, an unneeded calibration will actually make focusing less accurate.

    Does anyone actually KNOW anything about this? Or, as with everything else the major camera companies tell us, do we just swallow their “explanations” whole?

    * The autofocus sensor ALWAYS knows whether the two images are aligned or not. Therefore, the system SHOULD keep focusing the lens until they are, without any human intervention. You see a “gross” version of this when the initial focus is way off, and the AF continuously “hunts” without finding the correct point.

  2. Rich Meston

    Hi William

    What you say is correct about the AF system, but you have to remember that the AF sensor is separate from the image sensor. It’s housed in a different location, with a different optical path.

    The autofocus sensor will always lock (as best it can) to an in-focus image, but if – due to mechanical tolerence of the mount, lens misalignment and other factors – there is a significant difference in path length between the subject-to-af-sensor distance and subject-to-image-sensor distance, then the *image* captured will be out of focus.

    In reality, the distance to the AF sensor and the image sensor is different anyway, but this is calibrated out in the factory. Microadjustment allows for slight biasing of this distance per lens and per body.

  3. Fawaz Ayoub

    I think a lot of people forget that you can still using window applications on a Mac via 2 routes. Route 1 is obviously bootcamp and the use of BC with VM Fusion or Parallels. That route is more complIcated and I wouldn’t use it just for one program like this. Route 2 is probably one of my favorites and I use it all the time and that’s use a program called Crossover or you can use a free one called Wine and Wine Bottler to run windows applications without installing windows on your mac surprisingly they work amazingly well. I use them all the time and I actually recommend the free version called wine which also comes with wine bottler. They allow to run just about any windows application with no problem even games. Just to see how powerful it is I’ve even ran programs like Photoshop for windows and played 3D GPU and CPU intensive Games without and hiccups.

    I am almost positive you can run this application with no problem using wine and wine bottler. When I get home if I have time I’ll definitely test it out. Anyways I hope this helps because an application that does automatic AF Microadjust Calibration could be extremely useful.

    Hope this helps

  4. Andrew Gupta

    The concept is wonderful and I salute Reikan Photography for putting this together. My concern is that if you don’t get his setup done properly — you may get inconsistent results. Hence, I fear the pain-in-the-ass old fashioned manual method is not yet obsolete.

    Mr. Sommerwerck — The proper explanation is an essay. Getting “micro adjustment” correct is the difference between okay and magnificent images (when using autofocus). Respectfully I suggest you “google” it. Basically, if you think you’re getting soft results from a lens (when using autofocus) — you should explore micro adjustment.

  5. William Sommerwerck

    “What you say is correct about the AF system, but you have to remember that the AF sensor is separate from the image sensor. It’s housed in a different location, with a different optical path.”

    I think I stated the first part of that clearly. Regardless of where the sensor is located, it has to be in a conjugate image plane. If it isn’t, the image will be misfocused. (There are also the errors introduced by the fact that the sensor itself does not have infinite resolution, but those are presumably minor.)

    The mount’s tolerance has ABSOLUTELY NOTHING to do with focusing accuracy. If I stuck an inch-long extension tube (with all the electrical connections, of course) between a tele lens and the camera body, the system would still work correctly, because all it cares about is whether the image is in-focus at the sensor. If it’s in-focus there, it has to be in-focus at the image plane.

    I don’t know what you mean by “lens misalignment”.

    Pardon the mixed metaphor, but all I hear is a lot of hand waving. It isn’t at all clear why there should be a problem. This is typical of Japanese manufacturers… “Just do as we say, and everything will be all right.” Sorry, but I want to understand what’s going on. Is that too much to ask?

  6. William Sommerwerck

    Just to clarify a point… I am not in any way criticizing the software or its creator. That is not the issue.

  7. Rob

    William,

    As Rich explained to you, the fact that the image is focused on AF-sensor, does not necessarily mean that it is also focused on the imaging sensor. There is many possible factors that may throw those two sensors out-of-sync.

  8. William Sommerwerck

    Well, yes, I knew that. Nothing is perfect; all systems have tolerances. It just seems strange that the tolerance are so wide as to cause lenses to misfocus.
    ——————-
    After giving it some thought, I have what I believe is a correct explanation. Why >>I<< should have to explain this, and not Canon, is something I don't understand.

    When the image is not correctly focused on the focusing sensor, the sensor generates an error signal whose amplitude and polarity convey the magnitude and direction of the focusing error. This signal is amplified and drives the focusing motor until the error is so small (but not necessarily zero) that the driving voltage isn't enough to move the motor.

    There are two principal sources of the focusing error. One (of course) is the lens not being properly focused. The other is that the focusing sensor is not in the exact conjugate plane of the image sensor.

    Any physical displacement of the focusing sensor from the correct plane is fixed. So why isn't it possible to apply a static correction during the camera's alignment, and store it in the firmware? The answer is that the actual focusing error is not static — it varies with the lens's focal length, and the focusing distance.

    The longer the focal length, and/or the closer the focusing distance, the greater the error, because the image will be more "out of focus" for a fixed positioning error of the focusing sensor. (If this doesn't immediately make sense — it's for the same reason that long lenses have less depth of focus — the image goes out of focus more rapidly with shifts in the image plane.)

    I'm still trying to figure how aperture fits into all this. Nor is it clear why you shouldn't do this for all your lenses (though Canon says you're not supposed to, unless you see an obvious focusing error).

    At least I figured out part of it.

  9. Rob

    ‘Canon’ did its deed by providing a way to adjust misalignment.

    It is not feasible for the manufacturer to micro-adjust each and every lens in the factory. If they did that, the price of any lens would be much higher than it is now. Even ‘Leica’ does not do that.

    1. Mark

      But with Leica…you can return the lens and camera for it to be adjusted to deal with front or back focus…

    2. William Sommerwerck

      Rob, Mark… This is not a problem with the lens. It is a problem with the positioning of the camera’s focusing sensors.

      1. Mark

        My query is with the comment on returning the lens and camera to the factory for adjustment. With Leica – you can return them to Solms. Also, as you will be aware, the digital M series Leicas are manual focus.

        I am not trying to get into the discussion other than that.

        I will say that the only time I’ve had a problem with front/back focus…was with a Canon f1.4 50mm lens…on m 1 and 5 series Canons. I applied the microadjust for the lens only…and it focus’ perfectly now.

      2. Bengt Nyman

        Dear Reikan Photography,
        I applaud your efforts to develop this software.
        I have one question. Does your software establish front and back focus both and deliver the average or are you using strictly one or the other ?
        Or, perhaps your experience is that the difference is insignificant.

  10. William Sommerwerck

    I said nothing whatever about factory-adjusting the body (not the lens) for each and every lens. Please read what I actually wrote.

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