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Thread: EOS 5D MK3 underexposing by 1 or 2 stops - anybody else finding this?

  1. #11
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    Default Re: EOS 5D MK3 underexposing by 1 or 2 stops - anybody else finding this?

    I also own a 5D Mk III but have had no such problem. At first I thought it may be down to technique but you seem to have covered all bases!

  2. #12

    Default Re: EOS 5D MK3 underexposing by 1 or 2 stops - anybody else finding this?

    Ok, final update on this. Yes, I use the black rubber eye cover on tripod.

    Anyway, I bought an 18% grey card and stuck it on my wall and put camera on tripod, filled frame, put rubber eye cup cover in place and took a reading in Aperture Priority. I then went in to full Manual mode and chose the same shutter speed and aperture that resulted in my Aperture Priority reading and the little exposure meter digital needle was bang in the middle, so both exactly the same, as I'd expect them to be.

    When I then zoom out and point the camera to a different scene in the room, still the same wall and falling under the same light as the grey card, only now my kitchen table (which is pine wood and much lighter than 18% grey) with some items on it, the Aperture Priority mode now chooses a faster shutter speed, by about two stops, resulting in underexposure. If I then go back into Manual and use the same settings that were read off the grey card and re-take the image, it is perfectly exposed with a nicely balanced reading on the Histogram.

    The result of my findings is that all the metering modes on the camera: Evaluative, centre weighted, spot, etc, all underexpose by 2 stops on average for most of the scenes I shoot, landscape, portrait, buildings, anything outdoors. The only time I get a perfect exposure is doing studio strobe work with a flash meter.

    While doing this grey card test I also took two readings with my Sekonic L-308X meter in both incident and reflected modes and it came back with the same as the Canon, F4 with a shutter speed of 1/4th second at 100 ISO, which tells me all is good.

    I've deduced that I can only really use 'spot metering' with this camera and that I must aim the spot at something that is as close to 18% grey as possible and even then to check the histogram to make sure it is balanced and not all leaning too far to the left.

    Anyway, appears there is no fault, just the 5D MK3 is really fussy and there is no room for anything outside 18% grey as far as the cameras built in exposure sensor is concerned. But then again, built-in exposure meters that take 'reflective' light readings are never going to be spot on, but the Canon just seems to be very unforgiving, unlike my old Nikon D3s, which did a much better job.

    So, to re-cap, I just have to use spot metering and aim for subjects in the scene that look close to 18% grey and then hit the exposure lock button on the back of the camera, re-compose, take shot and check histogram.

  3. #13
    Member SpringfieldPhoto's Avatar
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    Default Re: EOS 5D MK3 underexposing by 1 or 2 stops - anybody else finding this?

    I had a 5D3 for a number of years and took 35,000 pictures using various modes and never had this problem. Sounds like a fault. Having said that I did find that Lightroom occasionally produced weird results with files from this camera but when processed in DPP there was no problem. Still think that you have a faulty camera.
    Alan

    2 5D Mk IVs, EOS 3, Canon 20mm f2.8, Sigma 35mm f1.4 Art, Sigma 50mm f1.4 Art, Sigma 105mm f1.4 Art, Canon 85mm f1.4, Tamron 24-70 f2.8, Sigma 70-200 f2.8 and Sigma 150mm f2.8 macro.

    http://www.springfield-photography.com/

  4. #14

    Default Re: EOS 5D MK3 underexposing by 1 or 2 stops - anybody else finding this?

    I agree, Alan. Will put up with it and work with Sekonic meter in the meantime as that is acurate.

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