Eratic focus

Discussion in 'Photography Beginners' Forum' started by tbrownarcher, Sep 22, 2007.

  1. tbrownarcher

    tbrownarcher TPF Noob!

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    I have a focus problem or I don't know what I'm doing. (oh! yeah! I don't ! ) :>)

    When I zoom in on a distant object such as a bluff or cloud bank or mountain my camera sometimes does and sometimes does not focus on it.

    I get better focus with the auto focus but that moves the focus point to the brightest or most prominent object so I set the auto focus to (SPOT). Now the AF box does not move but long distance focus is almost impossible.

    AF is unacceptable because of the AF box moving to the most prominent object.

    Is my camera broken? 'Olympus sp 550 uz' is the model

    Thanks,
    tbrownarcher (nate)
     
  2. The_Traveler

    The_Traveler Completely Counter-dependent Supporting Member

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    the auto focus needs a contrasty edge to focus well so clouds etc. may not do it.
    I'm almost certain that your camera will focus lock if you press the shutter halfway.
     
  3. ~Stella~

    ~Stella~ TPF Noob!

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    Am I the only person who misread and wondered WTF an "erotic focus" was? :confused:
     
  4. The_Traveler

    The_Traveler Completely Counter-dependent Supporting Member

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    I actually had my hopes up but they were quickly dashed.
     
  5. tbrownarcher

    tbrownarcher TPF Noob!

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    Traveler:
    No! The camera does not focus when at high zoom and pointed off in the distance. Not on clouds, not on hills, not on anything consistantly. Once in a while it does and more often in AF.

    But in AF the AF box is sent off to some other direction than the SPOT I want so I put the AF setting on spot and almost never focuses on the object or anything else in the frame.

    While taking a picture and while it's adjusting itself with the shutter butten held half down it goes through a point where the focus is correct but never stops there. This is all in 'P' mode I'm mentioning

    In Auto mode it does similar but more often but not nearly enough it gets a good picture. Most often it decides to focus on some object you are not interested in at all

    Thank,
    tbrownarcher (nateK)
     
  6. Garbz

    Garbz No longer a newbie, moving up!

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    This is the downside to the contrast based focusing system employed by point and shoot cameras. You need some sharp contrast in an image to focus correctly. It focuses by looking at the histogram of the image and adjusting the focus to get the widest one possible. The problem with landscapes is large areas of similar colours. Being in focus may not be evident looking at a histogram alone unless there are small contrasty patterns in an image which would be lost when something is out of focus.

    So in short, manual focus. If you can't manual focus see if there's something with enough contrast which is the same distance away to focus on and then recompose before you push the button all the way down.

    The_Traveler phase detectors are only used in SLR cameras. In this case a single edge in an image would be enough for autofocus.
     
  7. tbrownarcher

    tbrownarcher TPF Noob!

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    What exactly is a Point and Shoot as opposed to whatever the other is?

    Also, my camera has an 'M' setting. Can I focus manually somehow? I am not aware of any way to focus this camera manually even in the manual setting.


    thanks,
    tbrownarcher (Nate)
     
  8. Garbz

    Garbz No longer a newbie, moving up!

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    The M setting is for manual exposure control. There may be a manual focus somewhere else I really can't say without looking at the userguide myself.

    Point and Shoot is basically the category which lumps all non Digital SLR (single lense reflex) or professional digital rangefinders on this forum. Your olympus is categorised "SLR like" because of it's size and shape, but is still a P&S camera as it lacks the mirror and method of operation of SLR cameras.

    What this means for this thread is that an SLR camera uses a mirror and bounces the light into a pentaprism where it gets reflected into the viewfinder, and onto a very tiny 200-500pixel sensor dedicated to exposure metering and focusing tasks. A much smaller point and shoot cameras on the other hand work these functions based on the light currently hitting the main sensor and thus the specific workings and algorithms used are very different.
     
  9. tbrownarcher

    tbrownarcher TPF Noob!

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    GARBS:
    Yes I DO have Manual Focus. Next Time I need to zoom on some Clouds I will use it and see what happens .

    My Numbers on the screen for the focus slide start with 3 ft. and go to 16 ft. Then there is a little figure 8 squiggly charactar is that infinity??


    Thanks,
    tbrownarcher (nate)
     
  10. The_Traveler

    The_Traveler Completely Counter-dependent Supporting Member

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    yes
     

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