How/where does a DSLR sense light for metering?

Discussion in 'Digital Photography' started by Peabody, Mar 15, 2012.

  1. Peabody

    Peabody Guest

    Does it just measure the light intensity via the focus points, or
    is there some other mechanism involved? This would be in normal
    viewfinder mode, not liveview, so the sensor can't be involved.
    Peabody, Mar 15, 2012
    #1
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  2. Peabody

    nospam Guest

    In article <>, Peabody
    <> wrote:

    > Does it just measure the light intensity via the focus points, or
    > is there some other mechanism involved? This would be in normal
    > viewfinder mode, not liveview, so the sensor can't be involved.


    it reads it off the focusing screen. different cameras have different
    numbers of metering zones and may weigh them differently (spot,
    center-weighted, matrix, etc.)
    nospam, Mar 15, 2012
    #2
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  3. Peabody

    Ray Fischer Guest

    Peabody <> wrote:
    >Does it just measure the light intensity via the focus points, or
    >is there some other mechanism involved? This would be in normal
    >viewfinder mode, not liveview, so the sensor can't be involved.


    If you can peer into the front of a DSLR you might see a 2nd mirror
    behind the main one. The main mirror lets some light through where it
    reflects off of the 2nd mirror down to the focusing and exposure
    sensors.

    --
    Ray Fischer | None are more hopelessly enslaved than those who falsely believe they are free.
    | Goethe
    Ray Fischer, Mar 15, 2012
    #3
  4. Peabody

    nospam Guest

    In article <4f61635b$0$12018$>, Ray Fischer
    <> wrote:

    > >Does it just measure the light intensity via the focus points, or
    > >is there some other mechanism involved? This would be in normal
    > >viewfinder mode, not liveview, so the sensor can't be involved.

    >
    > If you can peer into the front of a DSLR you might see a 2nd mirror
    > behind the main one. The main mirror lets some light through where it
    > reflects off of the 2nd mirror down to the focusing and exposure
    > sensors.


    focus sensors are in the mirror chamber via the secondary mirror. the
    metering sensors are normally in the prism.

    <http://www.mir.com.my/rb/photography/hardwares/classics/NikonF5/meterin
    g/Sensorlocation.jpg>
    nospam, Mar 15, 2012
    #4
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