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Thread: A7s judders in continuous auto focus mode (AF-C)

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    A7s judders in continuous auto focus mode (AF-C)

    Hi all
    Bought my A7s on friday and have just noticed any issue when using continuous auto focus (AF-C) when I do half press of the shutter to lock and track focus the lens judders in and out for a few seconds and then will settle. Whenever I move the lens judders in and out again. Happens in all the 'focus area' modes (centre, zone, wide etc). Happens with all my sony/zeiss lenses (55, 35 and to a lesser degree with the 24-70)
    I have the A7 which doesn't do this but will lock (when it wants too) and doesn't judder in and out. I am wondering anyone with S can try this out to see what happens. Unfortunately my dealer has none available at the moment to test against

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Same here... Likely a result of the intelligence that controls AF-C and contrast based only auto focus?

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Interesting so this is a fault in the firmware or camera design. somewhat annoying and makes the camera useless in follow auto-focus. Will get back onto sony about it

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Have you tried to track a moving object towards and away from the camera? Is it the same?
    If you move your focus point from object to object while the objects are just still, I think the camera behaves normally in AF-C then.

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Not sure what you are saying but if I move and keep fixed on an object it keeps juddering in and out. have tried it out and it does seem actually to focussing accurately but surely this in a and out movement apart from being annoying just isn't right

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Will have to check it out.

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Quote Originally Posted by Viramati View Post
    Hi all
    Bought my A7s on friday and have just noticed any issue when using continuous auto focus (AF-C) when I do half press of the shutter to lock and track focus the lens judders in and out for a few seconds and then will settle. Whenever I move the lens judders in and out again. Happens in all the 'focus area' modes (centre, zone, wide etc). Happens with all my sony/zeiss lenses (55, 35 and to a lesser degree with the 24-70)
    I have the A7 which doesn't do this but will lock (when it wants too) and doesn't judder in and out. I am wondering anyone with S can try this out to see what happens. Unfortunately my dealer has none available at the moment to test against
    Viramati:
    When this happens are you in a very dark environment? It sounds like the AF is hunting for focus confirmation. Does it work better in full daylight?

    Regards,
    John

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    Re: A7s judders in continuous auto focus mode (AF-C)

    No this is happening in full daylight at base iso and high shutter speeds and is the same in low light
    Strangely the 24-70 doesn't seem to really show the effect but it is very noticeable with the FE35 and 55
    here is a link to a rather bad video but it shows the problem
    https://www.flickr.com/photos/viramati/15119219002/
    Last edited by Viramati; 2nd September 2014 at 10:25.

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    Re: A7s judders in continuous auto focus mode (AF-C)

    I checked with the 55 f/1.8. Focus locks in less than a sec. I did not notice any issue. Hope other users can chime in.

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Quote Originally Posted by sven View Post
    I checked with the 55 f/1.8. Focus locks in less than a sec. I did not notice any issue. Hope other users can chime in.
    Have you checked when using AF-C. normal focus lock is fine (that is AF-S)

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    Re: A7s judders in continuous auto focus mode (AF-C)

    yes I checked AFC, even with poor contrast subjects it does not judder, it searches focus and locks in a sec. Even in candle light it focuses in a second. It may hunt once but locks immediately. Nothing that lasts for several seconds.

    Btw, AFC is for moving subjects, so on stationary subjects it may change focus slightly as it anticipates to focus on movement of the subject but never lasts few seconds.

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    Re: A7s judders in continuous auto focus mode (AF-C)

    I can repeat your findings, just that my sample doesn't hunt that fast back and forth. Think it is object dependable?
    Tracking moving objects shows no hunting and I find the camera responds pretty fast.

    I guess Sven is right the AF-C is a kind of anticipation mode and the camera expects to detect changes in the focal plane.

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Thanks all for your replies. My dealer is getting another camera in for me and I will see if it is any better.

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Best thing to do.
    Likes 1 Member(s) liked this post

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Viramati, please let us know what's the outcome on your replacement camera. I recently got my a7s and have the same problem as yours. Mine takes about 2-3 seconds to lock focus in AF-C mode and judders same as the one in your video even on a well lit subject and aperture wide open using 55 1.8 FE lens. thanks

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Quote Originally Posted by oortega View Post
    Viramati, please let us know what's the outcome on your replacement camera. I recently got my a7s and have the same problem as yours. Mine takes about 2-3 seconds to lock focus in AF-C mode and judders same as the one in your video even on a well lit subject and aperture wide open using 55 1.8 FE lens. thanks
    will do

    By the way does the A7R show the same problem
    Last edited by Viramati; 3rd September 2014 at 23:14.

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    Re: A7s judders in continuous auto focus mode (AF-C)

    So I tried another one in store today and it does the same thing, also tried the A7r which does it but it would seem to a slightly lesser extent. Well I suppose I will have to live with it though I do find it a little off putting

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    Re: A7s judders in continuous auto focus mode (AF-C)

    I think then what's said about AF-C is executing an anticipation program and search for movements towards and away from the camera and hence the lense travels before lock.

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Thanks. Just strange that it doesn't happen on the A7 even in low light when it is using CDAF

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    Re: A7s judders in continuous auto focus mode (AF-C)

    Quote Originally Posted by Viramati View Post
    Thanks. Just strange that it doesn't happen on the A7 even in low light when it is using CDAF
    This is not related to A7s but the lens. I used a different copy of 55mm f/1.8 and sure did it judder. Now I understand what you meant. I swapped the lens for my copy (lens) and it did not do that.

    Btw. It is notable only in manual mode and AF-Continous. It is almost gone in AF-C and shutter or aperture mode. No judder in AF-S mode. So looks like the lens anticipates to try to focus anything that moves. Sorry if the info is too late to change the lens.

    Sven

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