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Thread: Auto-focus

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    Default Auto-focus

    I am using a Sony-DSC H2.

    When i zoom in (about 8-10X) i find the the auto focus is very unprecise and my pictures seem very out of focus. How do i go around the problem?

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    Senior Member zoossh's Avatar
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    Default Re: Auto-focus

    Quote Originally Posted by hairygorillaz View Post
    I am using a Sony-DSC H2.

    When i zoom in (about 8-10X) i find the the auto focus is very unprecise and my pictures seem very out of focus. How do i go around the problem?
    change a camera. it simply means that your camera's autofocusing mechanism cannot cope with difficult contrast situations.

    alternatively avoid shooting under those circumstances.

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    Default Re: Auto-focus

    i very much would like to change a camera too, but cash is a problem. So i have to stick with my H2 for the time being.

    One more question, when the camera says marco mode, wad distance range does it refer to?

  4. #4

    Default Re: Auto-focus

    hi,
    since it only happen to zoom out at 8-10 x, it might be your shutter speed that is not fast enough to produce a steady shot(I supposed you hand hold the camera?). two ways to verify this:
    (1) increase your shutter speed to at least 1/(focal length) or even higher.
    (2) use a tripod to steady the camera

    if 2 can produce a good focus shot, then the problem is not on the camera.

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    Senior Member zoossh's Avatar
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    Default Re: Auto-focus

    Quote Originally Posted by hairygorillaz View Post
    i very much would like to change a camera too, but cash is a problem. So i have to stick with my H2 for the time being.

    One more question, when the camera says marco mode, wad distance range does it refer to?
    i dun have the technical qualifications, but in principle, it is supposed to show up actual live size represenations on the live size sensor. but in reality, the definition of macro is hard to apply in that manner. for example, macro requires a 8mm subject to appear as physical 8mm image on any sensor, but it will fill up the whole of a 8mm sensor but as a quarter of the area on a 16mm sensor where the one on the smaller sensor looks as if they are bigger.

    i'm not familiar with the pns settings. but in general for macro, we either makes uses of change of optical centre by close up filters (magnifiers) or with closer focusing distance by extension tubes and macro lens. it appears that my tamron 90mm macro lens have a minimum focus distance of 29cm. but bear in mind, my sensor size is that of a normal DSLR sensor at 1.5x cf.

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    Senior Member zoossh's Avatar
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    Default Re: Auto-focus

    Quote Originally Posted by CT 3833 View Post
    hi,
    since it only happen to zoom out at 8-10 x, it might be your shutter speed that is not fast enough to produce a steady shot(I supposed you hand hold the camera?). two ways to verify this:
    (1) increase your shutter speed to at least 1/(focal length) or even higher.
    (2) use a tripod to steady the camera

    if 2 can produce a good focus shot, then the problem is not on the camera.
    i think you rightly point out something that i might have missed out. that maybe the ts's claims unprecise autofocus may not be actually autofocus issue.

    harry, do you noticed that your camera takes longer to achieve focus or zooms in and out of focus while AF is working? if it does, it is probably like what i say. but you should try out ct's suggestion which is more confirmative

  7. #7

    Default Re: Auto-focus

    Quote Originally Posted by hairygorillaz View Post
    I am using a Sony-DSC H2.

    When i zoom in (about 8-10X) i find the the auto focus is very unprecise and my pictures seem very out of focus. How do i go around the problem?
    It could be camera shake. Check those photos and see what was the shutter speed it was shot at. If the shutter speed is too low, you'll get blurred photos due to camera shake.

    BC

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    Default Re: Auto-focus

    i juz checked, exposure was about 1/60 secs. So i doubt is was due to camera shake

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    Default Re: Auto-focus

    Quote Originally Posted by Scaglietti View Post
    It could be camera shake. Check those photos and see what was the shutter speed it was shot at. If the shutter speed is too low, you'll get blurred photos due to camera shake.

    BC
    i remember H2 have sony super steady shot technology.
    try using the viewfinder to reduce chances of camera shake if you do not have a tripod.
    super zoom cameras have problems focusing in low light so is better to mount on tripod while shooting at night.

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    Senior Member zoossh's Avatar
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    Default Re: Auto-focus

    Quote Originally Posted by hairygorillaz View Post
    i juz checked, exposure was about 1/60 secs. So i doubt is was due to camera shake
    but are u sure of that? i'm not trying to be nasty but sometimes people can stil have handshake at that exposure duration. and how far did you zoom in? note that in long focal length, the requirement of shutter duration is even more demanding.

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    Senior Member zoossh's Avatar
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    Default Re: Auto-focus

    Quote Originally Posted by Simon_84 View Post
    super zoom cameras have problems focusing in low light so is better to mount on tripod while shooting at night.
    actually the concept is not correct.

    first point. super zooms can still cope well at its wide angle side, whereas a 500mm prime will have the same problem with a super zoom at 500mm end. the difference is in terms of optical quality due to lens element quality and design though.

    2nd point. focusing difficulty in low light is due to the ability to discern contrast difference, and not due to the focal lengths. what you meant is probably that it is difficult to do handheld shots at long focal length.

  12. #12

    Default Re: Auto-focus

    I just learned from the web that DSC H2's longest zoom is 432mm. If you extend the zoom all the way and take a shot at 1/60, then even wif a Vibration Reduction, one would still get a shaky shot.

    To be on the safe side, for verification purpose, you should AT LEAST shoot at 1/500 ior 1/640 for 432mm focal length.

    To be dead sure, I still strongly suggest that you should use a tripod or, at least place the cam on the table and take a few test shots. I tot this is very easily doable. Why not try it out and tell us the outcome.

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    Default Re: Auto-focus

    thanx for the feedback. tried it. its the focus. Still unable to focus. It can't even focus on the electronic viewfinder.

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    Senior Member zoossh's Avatar
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    Default Re: Auto-focus

    Quote Originally Posted by hairygorillaz View Post
    thanx for the feedback. tried it. its the focus. Still unable to focus. It can't even focus on the electronic viewfinder.
    why is meant by "focus on the electronic viewfinder"? you mean it can't even focus on the subject when you look at the electronic viewfinder or the LCD display before the shot is taken.

    perhaps you would like to show the pic so that we have an idea of how bad is the lack of contrast in your field of view.
    Last edited by zoossh; 5th May 2007 at 04:59 PM.

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    Default Re: Auto-focus

    yeps. i'm in the process of uploading the image

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    Default Re: Auto-focus





    ok. the first image shows the subject (The spiderman toy) its at about 4.5X zoom

    the second shows the zoom-ed in one. (9.xX)

    Its not camera shake as the red is still clearly defined.

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    Default Re: Auto-focus

    Quote Originally Posted by hairygorillaz View Post
    http://i120.photobucket.com/albums/o189/hairygorillazz/DSC01955.jpg
    http://i120.photobucket.com/albums/o...z/DSC01958.jpg

    ok. the first image shows the subject (The spiderman toy) its at about 4.5X zoom

    the second shows the zoom-ed in one. (9.xX)

    Its not camera shake as the red is still clearly defined.
    yes, no doubt its focusing problem... but from the look, it seems that it is user fault since you are trying to focus on something that is too near (not within the camera focusing range...)

    so you might want to think about it again before blaming on equipment..
    I believe most superzoom PnS have a minimum focusing of 3-5m when zoomed...

    and btw are you sure it is 9.xx zoom? it seems to be it is 45x zoom when compared to the 4.5x zoom pic.
    Last edited by ExplorerZ; 5th May 2007 at 05:31 PM.

  18. #18

    Default Re: Auto-focus

    Your first pic is also not sharp. And it looks more to me that the pic was taken with some degree of vertical hand shake.

    The second shot seem to be taken to close the focusing range that the camera can handle.

    Also make sure the subject surface has sufficient contrast, like vertical lines for the camera to focus on.

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    Default Re: Auto-focus

    Quote Originally Posted by CT 3833 View Post
    Your first pic is also not sharp. And it looks more to me that the pic was taken with some degree of vertical hand shake.

    The second shot seem to be taken to close the focusing range that the camera can handle.

    Also make sure the subject surface has sufficient contrast, like vertical lines for the camera to focus on.
    sorry, i dun understand that part about having sufficient contrast. could someone please elaborate

  20. #20
    Senior Member zoossh's Avatar
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    Default Re: Auto-focus

    Quote Originally Posted by hairygorillaz View Post
    sorry, i dun understand that part about having sufficient contrast. could someone please elaborate
    dun worry abt that. your image have sufficient contrast for auto-focusing. so that is not the case. it could be the minimal focusing distance (which means that you MUST stand further away from the subject) but i'm not familiar with pns or prosumer.

    have you have a photo that you can get a sharp picture on the tripod at say 5m from the subject, but got it blur on the tripod when you zoom in from the same standing position without moving the tripod and the camera?
    Last edited by zoossh; 5th May 2007 at 06:04 PM.

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