Check exposure digital Canon 20D

Discussion in 'Digital Photography' started by Jack, May 18, 2006.

  1. Jack

    Jack Guest

    Hi all
    How can I check the actual sensitivity of my camera a Canon 20D ?
    A bit difficult to explain but I'll try.
    When my light meter says 5.6 at iso 200. How can I check that my camera is
    the same and not out by +1 or -1?

    Thanks
    J
    Jack, May 18, 2006
    #1
    1. Advertising

  2. Jack wrote:
    > Hi all
    > How can I check the actual sensitivity of my camera a Canon 20D ?
    > A bit difficult to explain but I'll try.
    > When my light meter says 5.6 at iso 200. How can I check that my
    > camera is the same and not out by +1 or -1?
    >
    > Thanks
    > J


    Why not work on the results and not the trip. If you get the results
    you want, who really cares if the settings are off, as long as they are off
    in a way that produces the results. While there are situations where the
    difference would be important, most of us never had that issue so why worry,
    just continue to learn your tools and how they work for you. Setting a
    camera to 5.6 or 8.0 is not all that important as long as you know what you
    need to set it to.

    --
    Joseph Meehan

    Dia duit
    Joseph Meehan, May 18, 2006
    #2
    1. Advertising

  3. Jack

    Guest

    Joseph is right, but if you wish to agonise over it, buy/rent/borrow
    yourself a decent light meter, or check it against a known accurate
    camera.

    The latter is a very rare animal...
    , May 18, 2006
    #3
  4. "Jack" <> wrote in message
    news:...
    > Hi all
    > How can I check the actual sensitivity of my camera a Canon 20D ?
    > A bit difficult to explain but I'll try.
    > When my light meter says 5.6 at iso 200. How can I check that my
    > camera is the same and not out by +1 or -1?


    Try and measure the exposure for the reflection from a uniformly lit
    flat surface with both. If you set the camera focus at infinity, the
    results should be closest.

    Both will try and calculate an exposure that would render the surface
    as medium brightness, in line with the meter's assumption of what
    medium brightness is. Some meters will be calibrated for 12.5%, others
    might be calibrated for a higher subject reflection of about 18%, so
    that may cause half a stop difference in readout.

    Bart
    Bart van der Wolf, May 18, 2006
    #4
  5. Jack

    D Mac Guest

    Jack wrote:
    >> Hi all
    >> How can I check the actual sensitivity of my camera a Canon 20D ?
    >> A bit difficult to explain but I'll try.
    >> When my light meter says 5.6 at iso 200. How can I check that my
    >> camera is the same and not out by +1 or -1?
    >>
    >> Thanks
    >> J

    Canon DSLRs are not exact in their ISO rating. ISO 100 with my 20D is
    actually ISO 140 with my very accurate light meter. Somewhere in a dpreview,
    I remember reading about this in relation to other Canon DSLRs.

    Douglas
    D Mac, May 18, 2006
    #5
  6. "D Mac" <> wrote in message
    news:Qs6bg.6475$...
    SNIP
    > Canon DSLRs are not exact in their ISO rating. ISO 100 with
    > my 20D is actually ISO 140 with my very accurate light meter.


    Which meter would that be?

    Using the method I outlined earlier in this thread, my Canon EOS-1Ds
    Mark II gives the exact same readout as my Seconic L-408 at the same
    ISO , as does my EOS-20D. My method also produces a centered spike in
    the JPEG histogram.

    Whether that measurement produces the best possible exposure level
    (optimal non-clipped Raw exposure) depends on subject contrast and Raw
    overexposure latitude, which is the photographer's responsibility. The
    meter can't think in terms of contrast unless you take multiple spot
    readings.

    Bart
    Bart van der Wolf, May 19, 2006
    #6
  7. Jack

    Roy G Guest

    "Jack" <> wrote in message
    news:...
    > Hi all
    > How can I check the actual sensitivity of my camera a Canon 20D ?
    > A bit difficult to explain but I'll try.
    > When my light meter says 5.6 at iso 200. How can I check that my camera
    > is
    > the same and not out by +1 or -1?
    >
    > Thanks
    > J
    >
    >


    You can not tell, whether the camera is actually firing at the settings
    shown in the VF.

    You can tell if the shown figures are accurate, by using an accurate hand
    held meter, if you know what you are doing.

    The Actual Shutter Speed and Actual Aperture at which a Camera is operating
    could be tested on a Film Camera using an expensive piece of test equipment,
    with its detector placed in the Film Path.

    Any results which were within 10% of the set figures were considered very
    accurate.

    The really important result was that the shutter speed steps should be in an
    arithmetical progression. However many Msecs the shutter was open for
    125th, should be halved for 250th, and that the curtains should run at a
    fairly constant speed.

    Nikons tended to be the most consistent for shutter speed, but were nearly
    always almost half a stop under exposed when the metering was measured.

    But, of course, there is no way of doing anything like this with a Digital
    Camera without removing the Imaging Sensor.

    Roy G
    Roy G, May 19, 2006
    #7
  8. Jack

    Roy G Guest

    "Jack" <> wrote in message
    news:...
    > Hi all
    > How can I check the actual sensitivity of my camera a Canon 20D ?
    > A bit difficult to explain but I'll try.
    > When my light meter says 5.6 at iso 200. How can I check that my camera
    > is
    > the same and not out by +1 or -1?
    >
    > Thanks
    > J
    >
    >


    You can not tell, whether the camera is actually firing at the settings
    shown in the VF.

    You can tell if the shown figures are accurate, by using an accurate hand
    held meter, if you know what you are doing.

    The Actual Shutter Speed and Actual Aperture at which a Camera is operating
    could be tested on a Film Camera using an expensive piece of test equipment,
    with its detector placed in the Film Path.

    Any results which were within 10% of the set figures were considered very
    accurate.

    The really important result was that the shutter speed steps should be in an
    arithmetical progression. However many Msecs the shutter was open for
    125th, should be halved for 250th, and that the curtains should run at a
    fairly constant speed.

    Nikons tended to be the most consistent for shutter speed, but were nearly
    always almost half a stop under exposed when the metering was measured.

    But, of course, there is no way of doing anything like this with a Digital
    Camera without removing the Imaging Sensor.

    Roy G
    Roy G, May 19, 2006
    #8
    1. Advertising

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Your name

    Can't Open RAR files - PAR check ok, SFV check ok

    Your name, May 9, 2005, in forum: Computer Support
    Replies:
    3
    Views:
    8,405
  2. Diane H. Boehm

    Canon EOS Digital Rebel - Exposure Problems?

    Diane H. Boehm, Jan 5, 2004, in forum: Digital Photography
    Replies:
    11
    Views:
    1,743
    Kevin McMurtrie
    Jan 11, 2004
  3. S. S.
    Replies:
    3
    Views:
    526
    Dave Martindale
    Jun 24, 2004
  4. Martin
    Replies:
    8
    Views:
    303
    Skip M
    Aug 30, 2005
  5. Replies:
    2
    Views:
    812
Loading...

Share This Page