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Olympus ISO accuracy

Discussion in 'Olympus Cameras' started by JJJPhoto, Jan 29, 2013.

  1. JJJPhoto

    JJJPhoto Mu-43 Veteran

    252
    Jul 8, 2011
    Cincinnati, OH
    Jerry Jackson Jr
    Although I'm not a huge fan of DxOmark since it reduces photography down to raw numbers, I recently became concerned when I noticed that DxOmark is reporting that Olympus camera ISOs aren't as accurate as other cameras:

    i-xtzqmqh.

    This isn't a scientific test, but I have both the Nikon D3100 and Olympus OM-D E-M5 so I put the Olympus 45mm 1.8 on the Olympus and the 85mm 1.8G on the Nikon and set them both to Aperture priority at f/1.8 and ISO 1600 with AWB. I then spot metered the same subject in my office with room light only (both cameras suggested the same shutter speed of 1/80th sec.) and took the photos. I shot handheld so excuse the minor difference in composition.

    Nikon:
    i-mBvk7NZ-L.

    Olympus:
    i-spSR49q-L.

    If the Olympus ISO was as low as what DxOmark claims the camera meter should have suggested a slower shutter speed or the Oly shot should have a darker exposure.

    I'd say both cameras delivered essentially the same exposure. I shot the Oly in JPEG mode with a custom curve to reduce contrast -- to prevent highlight/shadow clipping -- so that is why it looks less contrasty than the Nikon shot which was set to the default curve, but it's worth mentioning that the Olympus shot has sharper detail in the face of the monster model thanks to the IBIS and the Nikon shot has a hint of motion blur due to the lack of image stabilization.
     
  2. Djarum

    Djarum Super Moderator

    Dec 15, 2009
    Huntsville, AL, USA
    Jason
    I believe DXO mark looks at ISO right off the camera. Olympus generally underexposes the ISOs and then pushes digitally to make it appear as the correct ISO. While Shutter and Aperature were the same, I'd bet the RAW from the Nikon isn't as pushed as the RAW from the Olympus.
     
  3. macalterego

    macalterego Mu-43 Veteran

    228
    Jul 10, 2012
    Lawrence, KS
    Jeffrey McPheeters
    Is it also possible that Olympus is taking into account the wider dynamic range in order to accomplish the same result in exposed IQ? And I wonder if this is related to what I experience when using manual, adapted, legacy lenses on the E-M5 as it seems to want to over-expose, at least in my opinion, a scene compared to what native, electronic lenses will? I'm not sure if that isn't just a function of the metering, though. I'm not sure how much the camera and lenses coordinate settings.
     
  4. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    I doubt it. When I still had my D700, I tested using dcraw and Nikon uses exactly the same approach that Olympus does to get DR in the highlights - underexpose by 1 stop, push by 1 stop in the RAW converter.

    Of course, at the time Olympus was still using the 12MP Panasonic sensor, so that was a lot more objectionable than it is now.
     
  5. b_rubenstein

    b_rubenstein Mu-43 All-Pro

    Mar 20, 2012
    Melbourne, FL
    When the DxO review first came out, Ctein, (look for it here: The Online Photographer) addressed this issue in Why Doesn't Mean What You Think It Does (or something like that).
     
  6. Djarum

    Djarum Super Moderator

    Dec 15, 2009
    Huntsville, AL, USA
    Jason
    If this were the case, wouldn't DXO have shown that Nikon was a stop off like the OMD shows? Unless I'm missing something else here..
     
  7. flash

    flash Mu-43 Hall of Famer

    Apr 29, 2010
    1 hour from Sydney Australia.
    Gordon
    I don't see the big deal here. Canon have been electronically pushing their intermediate ISO's for years. Fuji Velvia was closer to ISO 40 than 50. Once you learn how the metering system works you just go out and use it, don't you? The only time I can see this as an issue is if you're using a handheld meter. But even then the decent ones have an offset function.

    Is there something I'm missing here or is this just another exercise in pixel peeping?

    Gordon
     
  8. b_rubenstein

    b_rubenstein Mu-43 All-Pro

    Mar 20, 2012
    Melbourne, FL
  9. JJJPhoto

    JJJPhoto Mu-43 Veteran

    252
    Jul 8, 2011
    Cincinnati, OH
    Jerry Jackson Jr
    I guess that's yet another reason for us to ignore DxOmark ... seems strange to show raw data if it doesn't mean what people would logically expect it to mean based on the way it is presented.
     
  10. HappyFish

    HappyFish Mu-43 Top Veteran

    983
    Sep 8, 2012
    Chad
    IMHO the OMD is a stop off ? Oh well still a great camera
     
  11. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    I don't think they're measuring ISO in the same way that we're using it. But my point is simply that this underexposure 'trick' is more or less de rigeur at this point. It also explains why ETTR, done carefully, produces significantly cleaner shadows on a lot of these newer cameras (e.g. something that shows as clipped on the LCD really isn't).