different types of metering

Discussion in 'Beyond the Basics' started by cameramike, Nov 13, 2007.

  1. cameramike

    cameramike TPF Noob!

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    So, maybe i'm just stupid but i can't seem to understand the different types of metering. On my camera (canon xti) i have the options of evaluative, partial, center - weighted average metering. so pretty much when would you use what?
     
  2. SpeedTrap

    SpeedTrap TPF Noob!

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    evaluative- Uses the whole frame, all the light the camera can see and averages it to get the exposure
    partial - Uses onlly the center 50% or so of the frame to meter, this will give more detailed results depending on the metering
    center - this uses a small spot in the center to meter from, this is the most exact but if used wrong will cause bad photos.

    Go outside and try to meter on differnt thins like a tree in the shade and a tree in the sun on each setting and look at the differences.
     
  3. usayit

    usayit No longer a newbie, moving up!

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    Not quite....

    Your manual has a good explanations of each mode...

    Evaluative: Sensor is divided into several "zones" and measurements are sent to the to the internal processor which maps it to an exposure.

    Partial: 9% of the center

    Center: weighed towards the center and averaged throughout the rest of the viewfinder.
     
  4. usayit

    usayit No longer a newbie, moving up!

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    I use mainly spot (it gives me the control I like) or center weighed (traditional on many cameras.. just comfortable with it).

    If spot is not available on the camera, then partial.
     
  5. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Evaluative or matrix metering divides the scene into different areas, and assigns levels of priority to each area. In general photos tend to be composed with important subject matter somewhere near the middle so those areas have more influence on the meter's recommendation, and less important stuff is at the edges so those areas are considered less. They are programmed to consider that often there's bright sky near the top, dark ground at the bottom, and a human face in the middle. Each manufacturer has spent way more money on advertising their fancy evaluative or matrix pattern than they did researching it.

    Partial metering means the meter is only considering an area in the center of the viewfinder. Spot metering is the same, but the area is even smaller for precise metering of smaller areas.

    Averaging metering is the ancestor of matrix/evaluative metering with only 2 or 3 areas instead of eleventy-twelvish areas. Center weighted means the area in the center has more influence.

    In the end the meter is still a very dumb machine that is trying to make your photo come out as close to middle gray tone as possible. It has absolutely no way of understanding how important various parts of the scene are to the photographer, or even what it in front of the camera.

    I find that evaluative metering usually works fine. For scenes where the edges are significantly brighter than the subject, such as back lighting, center weighted or partial might do a better job. I usually don't need to switch to another metering mode, because I understand the limitations of my metering pattern, and can adjust exposure accordingly. Although partial or spot metering can be handy when trying to measure specific small areas of the scene. I used it a lot when shooting film to count the stops between important shadow detail and important highlight detail to assess a developing plan. With digital I'm shooting raw (which allows developing by inspection), and just assess the histogram with a test shot.
     

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