Discussion in 'Olympus' started by phi_nevius, Jan 31, 2014.

  1. Hey,
    I've been having fun with my OM-D for the past month or so, and decided to test drive the new firmware v2.0, specifically the ISO LOW mode caught my interest.
    I've seen EM-1 posts showing detail advantages to shooting in ISO LOW in addition to reduced noise, and was curious if this would be true on the EM-5 as well.
    I did a quick semi-scientific test in my office, and it looks like ISO100 is identical to ISO200 +1EV corrected back down a stop. I knew this was a fake ISO and the EM5 "true" sensor ISO was always more like ISO105 base, so no surprises here.
    The histograms in LR5 and in camera are completely identical in ISO LOW or at ISO200 with +1EV, highlights blow out in the exact same places.
    For best detail and results, I think I'm still going to shoot ISO200. Looks like I'll be investing in some ND filters.
    There doesn't appear to be any detail advantage, but just in case anyones curious about it and considering upgrading their firmware I posted my test images:
  2. Thanks Phil, that's very helpful. Being a simple soul, I'll stick to using ND filters. If there's no beneficial effect on noise or DR, there seems little point in this part of the new firmware.
  3. Nice test!. I have had a couple of cameras with 'low' and have found through casual use that thtere was no advantage IQ wise. And typically that is what you would expect. I have used it with the EM1 when shooting conditions have warranted it but have not tested it like you did. DXOMark's measurements indicate there is slight improvement at ISO100 (which I was surprised to see) but it is slight and would likely not be visible in any test prints. Where have you seen EM1 test shots showing the differences between LOW (ISO 100) and ISO 200?
    When I first received my D800 (I was using the D3 at the time), I did some side-by-side DR comparison shots to see what the increase DR range of the D800 would give me over the D3. I could barely see the difference (yes there was a bit of a difference) even though on paper it was considered a reasonable difference. Since then, I have not worried about it. I find if I need expanded DR, I simply underexpose and adjust the levels during post processing.
  4. Bruce, interestingly, DXO shows the LOW setting on the EM1 not to be 100 either. In fact, they show both LOW and ISO 200 to be ISO 122. And more interestingly, they show ISO 200 on the EM5 to actually be ISO 107. They do not show a test for ISO LOW on the EM5.
  5. Brice, did you read this bit further down the page?
    "I have realized I made a mistake when analyzing the RAW files to determine the relative exposure: the gap of 1/3EV is correct but... ISOLOW is the file with higher RAW values!...

    ...I.e. when you shoot using the same aperture and shutter at ISOLOW, you get RAW data 1/3EV more exposed (confirmed) than at ISO200."
  6. ^ Ooops, typo alert. Brice should read Bruce of course :)
  7. Brice [sic], did you read this bit further down the page?​
    I read all the posts in the thread at the time I linked to it. I have no idea what point you are attempting to make.
    The important concept is not whether the E-M5 LOW is a true 100 ISO, but that most people don't understand what ISO really means or how it's determined. BJL's post is the most important in the thread: No, that is belief is based on misinterpretation of the fact that EM5 raw files have more than the _minimum_ highlight headroom specified by the ISO standard for minimum or base exposure index, so that the _base ISO speed_ is less than the lowest ISO exposure index setting. It is nothing to do with the camera giving more exposure than specified by the ISO exposure index setting. People who study those DXO measurements really need learn the differences between the various different measurements of sensor characteristics defined by ISO standard 12232, and avoid referring to them all as simply "ISO".

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