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Autofocus calibration - Am. Photographer magazine

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    Sus
    Sus  93183 forum posts England9 Constructive Critique Points
    3 Jun 2011 - 10:52 AM

    AP are giving away a free calibration tool for autofocus this week. Would this be useful? I sometimes have problems with AF but more in the AI Servo and AF tracking modes.

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    3 Jun 2011 - 10:52 AM

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    Overread
    Overread  63763 forum posts England18 Constructive Critique Points
    3 Jun 2011 - 10:56 AM

    The focus chart (I'm assuming its one of them since its the only tool I know for AF calibration) is quite simple. Its little more than a ruler in design. The idea is that it gives you a measurable scale - you set it at 45 degrees to your camera and then use the AF to focus in single point AF mode. Then you can compare the results and see if the camera is setting the focus on the line or if its mostly before or after the len (Back or front focusing) and thus letting you set a calibration for AF micro adjust in your camera (if your camera supports this).

    Sus
    Sus  93183 forum posts England9 Constructive Critique Points
    3 Jun 2011 - 10:59 AM

    Does that mean I could do the same thing with a standard ruler?

    JackAllTog
    JackAllTog e2 Member 53626 forum postsJackAllTog vcard United Kingdom58 Constructive Critique Points
    3 Jun 2011 - 11:03 AM

    It folds up to look like a triangular sandwich carton and had the ruler printed on the sloping face. The instructions for use are printed inside the magazine. You have to have the lens quite far away from the calibration tool, a reciprocal distance of about 2 - 3 metres i think for a 50mm lens. (i assume the crop multiplier applies here too).
    It was also more critical for long (or short) lenses to be adjusted correctly - arrgh i can't remeber which - sorry.

    I can't micro adjust my 60D, so all i'd know is if my lenes are close or not. I'll try it if i can find time.

    User_Removed
    3 Jun 2011 - 11:05 AM

    I got one with last week's AP and tried it. Quite re-assuring of nothing else.

    Sus
    Sus  93183 forum posts England9 Constructive Critique Points
    3 Jun 2011 - 12:13 PM

    Just checked and it seems I can microadjust the 5DII.

    http://www.northlight-images.co.uk/article_pages/cameras/1ds3_af_micoadjustment.html

    i'll give it a go, if this article doesn't work I'll get AP. Thanks for info about it (would have been annoying if I'd got it and not been able to microadjust - I assumed all cameras would be able to!)

    Overread
    Overread  63763 forum posts England18 Constructive Critique Points
    3 Jun 2011 - 12:26 PM

    Micro adjust is, far as I know, only in the 50D, 7D, 5DM2 and the 1DMIV. I don't think any other cameras in the line have the feature (far as I know the 50D was the first to have it). You can still test your lenses and if you find one way out test it again to make doubly sure (because if its AF is way out chances are you should have noticed fairly soon) and then send the lens into canon for calibration (ideally you'd send lens + camera body in - also note that, as far as I know, lens calibrations are free under warranty - of course only whilst the warranty is valid).

    mikehit
    mikehit  56460 forum posts United Kingdom9 Constructive Critique Points
    3 Jun 2011 - 4:17 PM

    If I understand correctly, for zoom lenses micro-adjust is only valid for one specific focal length - so if you correct one focal length you risk putting another focal length out of kilter. The best thing is to send the lens for recalibration.

    User_Removed
    3 Jun 2011 - 4:29 PM


    Quote: Does that mean I could do the same thing with a standard ruler?

    Essentially - yes. Just be sure that the ruler/graduation sheet (they are available on the net) is at 45 to the horizontal and that you have some form of vertical focus 'target' adjacent to the middle of the ruler and off you go.

    Works a treat! Smile

    Sus
    Sus  93183 forum posts England9 Constructive Critique Points
    3 Jun 2011 - 8:10 PM

    I'll try that, thanks! But maybe I should read up more on micro-adjust, I don't know if I want to mess with it, given that.

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