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Thread: Canon 50D AF Microadjustment

  1. #1
    Jonathan Michael Ashton
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    Default Canon 50D AF Microadjustment

    I have just received my 50D back from repair - something was wrong with the circuitry. Having got it back I was wondering if I should consider AF adjustment for my lenses. The handbook appears to offer a warning so I am a little wary. Hitherto I think focus has been OK but of course I do not know if it could be better, I was wondering if anyone has made adjustments and how it was done.
    I guess you point at a high contrast target then go to Custom function 111 - 7 but then how do I know what adjustments should be made - does the camera indicate what I should dial in?

    Any advice would be welcome, thanks

    Jon

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    I certainly won't profess to be a tech guru, but here's how I approached it with my 50d. I visited this site www.rawworkflow.com/lensalign/ and watched the videos. i did not purchase the pro or lite version of the unit. I did have a 0 center rule on hand and made a focus target on some foam board. I clamped the zero center rule at an angle similar to what was in the video being sure that the 0 was in the same plane as the focus target. I then proceeded as I had seen in the video using live view. When finished with each lens, I took a shot and transfered it to my computer and blew it up to verify results. As for the results, it showed my 100-400 canon L was front focusing by 11 on the scale. My 24-105 was front focusing by 5. The amount to change the setting is guesswork and you'll need to repeat the procedure several times as you dial it in. Like I said, I'm no expert on this and others may say I'm completely wrong with a home made approach, but it's worked so far.:) There's no icon for "Fingers crossed" :D

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    My simple approach which worked for me using the MKIII and respective lenses was: I taped a $100 bill to a board. Then took frames at every +/- increment. Noted on a pad which file # corresponded with which setting. Looked at all the files at 100% and just went with the one I felt was most in focus.

    I am no tech expert either but it seems to have worked as I noticed the most improvement doing this with the EF500.

  4. #4
    Jonathan Michael Ashton
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    Thank you Dave & Mike

    Jon

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    Quote Originally Posted by Mike Tracy View Post
    My simple approach which worked for me using the MKIII and respective lenses was: I taped a $100 bill to a board. Then took frames at every +/- increment. Noted on a pad which file # corresponded with which setting. Looked at all the files at 100% and just went with the one I felt was most in focus.
    If you use DPP to review your files and press CTRL-I to display the EXIF information you can see the MFA value displayed. There is no need for any laborious note taking.

    Here's a screen print from DPP, reduced in size to fit for inclusion here. You can just make out the value of "AF Microadjustment : 1" over on the left, near the bottom.

    EDIT : I've added a better view of the info panel.




    The focus target you see is one made from Tim Jackson's design as described here....

    http://www.focustestchart.com/focus12.pdf

    There is an updated and simpler version described here....

    http://www.focustestchart.com/focus21.pdf

    In my opinion this target (especially the original) is every bit as good as the Lens Align Tool, albeit rather less sturdy, but at a small fraction of the price - about 1%, give or take. The videos on the LensAlign website are quite handy to demonstrate how to use the LensAlign Tool, but apply very well to the older and very much cheaper paper version that was published several years ago.
    Last edited by Tim Dodd; 02-23-2009 at 06:12 AM.

  6. #6
    Jonathan Michael Ashton
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    Thanks Tim, I have in fact been provided with a test target and I have calibrated all my lenses, but thank you for taking the time and trouble to be of assistance.

    Jon

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    I didn't do it in DPP but that affirms my claim I am not a expert.

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    Lifetime Member Doug Brown's Avatar
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    For the record, I've never had to perform a microadjustment on a lens. That includes a 600 f/4, 2 500 f/4s, 2 400 f/5.6s, a 70-200 f/2.8, and a 70-200 f/4. I've had recent conversations on this topic with both Artie Morris and Jim Neiger; neither of them has ever had to do a microadjustment either. Unless there's something obviously wrong with the focus of a lens, I'd be reluctant to do the microadjustment.
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    Clearly if you don't think you have a focus problem there is no benefit to be gained by fiddling without purpose - if it ain't broke, don't fix it etc. etc.. But, if you want to just try out an adjustment it is easily undone - just set the adjustment back to 0 for each lens or simply turn it off altogether.

    From my own experience, a lens/body combination may well deliver adequate results but that does not mean there is no room for improvement. FWIW here are samples from my AF calibration efforts with my 1D3 and 100-400. The first image is with 0 adjustment, clearly showing front focus, and the second image is with an adjustment of +7. I could observe the focus point gradually being pushed back with each increment of 1 to the adjustment value. These are 100% crops with sharpening set to 3 (out of 10) in DPP.

    No adjustment :




    Adjustment = +7 :



    In truth I may even need to push the focus back a little further still, perhaps to +8, but +7 is where I'm at for now.

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    FWIW this is Canons Chuck Westfall's take. I can't find the article I referenced for myself two years ago but this is from last December. 2nd question down. http://www.digitaljournalist.org/iss...tech-tips.html

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    I agree with Tim Dodd's comment "a lens/body combination may well deliver adequate results but that does not mean there is no room for improvement."

    My 50D/500mm F4 combination needed a +13 correction using an angled grid to determine the amount of correction. With the 1.4x TC, it only needed +7. I feel that at the magnitude of >10 it is well worth the trouble to correct it. I doubt if you can really tell the difference in the "correct setting" within in 1 or 2, but it is worth finding out if your setup has a significant problem. Since there is the potential of making things worse, I'd recommend taking your time and using the angled grid method. My initial attempt using something akin to the dollar bill technique missed the best value by 5, but showed that a correction might be in order

  12. #12
    Don Saunders
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    I used the LensAlign Pro to test and calibrate my lenses as necessary for both my 50D and 5D2. Some lens/body combinations did benefit from tweaking. The LensAlign Pro was easy to use and precisely align to the film (sensor) plane and is reproducible if needed.

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    Quote Originally Posted by Doug Brown View Post
    For the record, I've never had to perform a microadjustment on a lens. That includes a 600 f/4, 2 500 f/4s, 2 400 f/5.6s, a 70-200 f/2.8, and a 70-200 f/4. I've had recent conversations on this topic with both Artie Morris and Jim Neiger; neither of them has ever had to do a microadjustment either. Unless there's something obviously wrong with the focus of a lens, I'd be reluctant to do the microadjustment.
    If you can sort the wheat from the chaff and the facts from fiction in this discussion thread about DSLR autofocus design/operation....

    http://forums.dpreview.com/forums/readflat.asp?forum=1019&thread=31031173&page=1

    then I think you might agree that if your body/lens requires no calibration whatsoever then either you are very very lucky or perhaps not looking quite hard enough. I sincerely hope you are very very lucky :)

    I didn't think my lenses needed adjustment, based on results from my 30D and 40D, but then I never put them through any rigorous testing for AF accuracy. If I was satisfied with the images then that was enough. As the alternative was to send the whole caboodle off to Canon I was content to live with that level of satisfaction. When I bought my 50D, and later my 1D3, I thought I'd see whether there was any benefit to be gained by checking/adjusting the AF on those bodies. It appears that there was.

    When your glass isn't long enough and you're scrapping for every last drop of IQ from heavily cropped image files having that focus nailed to the mm becomes pretty important. If, on the other hand, you are consistently filling the frame with your subject then I'm sure a slight focus error is no big deal. On a wide open 100-400 @ 400, with or without a teleconverter, you want to grab any advantage you can that will improve the image captured.

  14. #14
    Robert Amoruso
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    I have done the adjustments with my 50D and Mark III and it is worth it. Up next is my 5D Mark II. Thanks for all the useful info Tim.

  15. #15
    Alfred Forns
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    Quote Originally Posted by Doug Brown View Post
    For the record, I've never had to perform a microadjustment on a lens. That includes a 600 f/4, 2 500 f/4s, 2 400 f/5.6s, a 70-200 f/2.8, and a 70-200 f/4. I've had recent conversations on this topic with both Artie Morris and Jim Neiger; neither of them has ever had to do a microadjustment either. Unless there's something obviously wrong with the focus of a lens, I'd be reluctant to do the microadjustment.


    Doug when Artie got his first Mk3 ALL his lenses were calibrated !!!!! Don't know if he continues doing the adjustments?

    I did calibrate with the Mk3 but it was a pain With the info Tim just gave I might go back and try it again. As I remember the biggest pain had to be writing the info !!!

    Something I'm not sure is that it would make that much of a difference in real world shooting? The way the AF points moves on the eyeball area of a bird will make a bigger difference. Perhaps would be good to test to see if any of them are way off !!!

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    Doug -

    I believe that in his Mark 3 User Guide, Artie describes one of his 500mm F4 lenses needing a significant correction (15-20) .

    The 50D and Mark 3 user manuals never give a definition of what each adjustment step represents. This was however defined in the technical White Paper for the 1 D Mark 3. Each step corresponds to the value obtained by multiplying the single sided DOF of a lens at maximum apeture by 1/8. Doing the math, for a 500mm f4 lens: at about 20' each adjustment step moves the focus point about 1/16" while at about 100' each step would move the focus point about 1.5". Theoretically, for any lenses with significant corrections , this distance would be greater than the distance the AF point moves on the eyeball of a bird.

    When i tested my 500mm F4, it needed about a +10 correction. Since the feature is there , it can't hurt to test your equipment.

  17. #17
    saleeltambe
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    I would like to know if the microadjustments carried out for 500mm/f4 would still stay the same if I use an additional 1.4x converter with this 500 f4 or will I need to do a separate microadjustment for 500mm + 1.4x combination ? Any inputs in this regard will be very helpful -Thanks.

  18. #18
    Alfred Forns
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    Need to do the same adjustment for the converters !!!!!

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    BPN Viewer Ed Grella's Avatar
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    Is this a Canon only tweak/fix?

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    Quote Originally Posted by saleeltambe View Post
    I would like to know if the microadjustments carried out for 500mm/f4 would still stay the same if I use an additional 1.4x converter with this 500 f4 or will I need to do a separate microadjustment for 500mm + 1.4x combination ? Any inputs in this regard will be very helpful -Thanks.
    I need a different adjustment with my 1.4X fitted to my 100-400. This only applies to my 1D3 as my 50D won't focus if it sees the teleconverter in place, at least with my 100-400 so it's a bit moot.

    If I was in the habit of putting the teleconverter on my 70-200/2.8-IS then I would need to check and calibrate that independently with and without the teleconverter. So long as the camera can see the teleconverter - i.e. it has the necessary pins and they are not taped - it will remember the adjutments individually for lenses with/without the converter.

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    Quote Originally Posted by Peter Kes View Post
    ...Where as the adjustments are great for the 4m distance, at 20-30m the focus turned bad (read: worse than before without the adjustments). ...
    According to canon, you need to calibrate it at 50X the focal length. so with a 400mm lens, you need to be 20 meters away from your target. It worked like a charm on my 50D.
    Dug

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    Quote Originally Posted by Dug Threewitt View Post
    According to canon, you need to calibrate it at 50X the focal length. so with a 400mm lens, you need to be 20 meters away from your target. It worked like a charm on my 50D.
    Dug
    For a general calibration, in the absence of any specific, known shooting distance then I do believe 50X FL (as a minimum) is the recommended distance.

    However, they also say that you should calibrate at the distance at which you expect to use the lens. You may even end up with different calibrations for different distances. e.g. if you intend to remain camped out 5.5m from your bird feeder then you may as well calibrate at 5.5m for the very best results there. If you use your lens at all ranges from MFD to tens of meters away then 50X FL is probably the best overall compromise.

    Note this extract from the 50D manual....

    1. It is best to make the adjustment at the actual place to be photographed. This will make the adjustment more precise.

    2. With setting 2, if an Extender is used, the adjustment will be registered for the lens and Extender combination.
    For item #1, I take that to mean that the calibration should be performed at the distance at which you intend shooting, rather than at some arbitrary distance such as 50X FL or, as some people tend to do (usually wrongly) at or close to the MFD. I don't see any reason why the lighting conditions should affect the calibration but let's not be too quick to dismiss that notion either.

    (I left item #2 in the quoted text because the question arose earlier.)

    I have carried out a calibration in the field with reasonable results. So long as you have a static, high contrast target available, with good/sharp detailing on it (perhaps tree bark) and a tripod (and a few minutes to spare) you should be able AF on the target and then switch to Live View, zoom in to 10X and review whether the focus is good enough or not. If not, focus manually just a tiny amount and see which way you have to turn the focus ring to sharpen the image. If you have to turn the ring clockwise (viewed from behind the camera) then you are having to bring the focus closer, which means the camera AF was back focused. You'll need to set the microfocus adjustment to a lower figure, perhaps negative or even more negative to improve things. Clearly if your image becomes sharper by turning the focus ring to anti-clockwise then you are having to move the focus further back. The AF has front focused so you need to add to the microfocus adjustment value to improve matters.

    I've read that if Canon calibrate the lens they can actually calibrate it for a range of distances and, in the case of a zoom, focal lengths. This will update a chip within the lens itself so that the lens knows how it performs. This is quite a step up from the relatively crude and simplistic microfocus adjustment option. If your lens is all over the place then it sounds like a trip to Canon is in order. If one adjustment is sufficient to meet your needs then you can take care of things easily enough yourself.

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