• Members 137 posts
    April 11, 2023, 6:08 p.m.

    But not in all cases. Using “DR” modes typically alters the ISO implementation and substitutes the analog amplification before the ADC, for brightening in the jpeg processing after the ADC to improve the highlight headroom. Whatever ISO Implementation is being used, it won’t usually determine the brightness of the processed raw file anyway, so while whatever ISO value you shot with might affect the raw file in some way, it really doesn’t apply to the raw file in that way (which is what the ISO standard is all about).

  • Members 457 posts
    April 11, 2023, 6:40 p.m.

    DR modes underexpose for a given ISO (by lowering ISO internally) and then brighten the image while preserving highlights. Even in DR modes, increasing ISO can cause raw clipping. In my book, that means that ISO settings apply to raw files.
    The only situation where ISO does not apply to raw files is when the ISO setting causes only a tag change (some cameras at higher ISOs, ISO bracketing in some cameras) and leaves the raw data unchanged.

  • Members 976 posts
    April 11, 2023, 6:46 p.m.
  • Members 137 posts
    April 11, 2023, 7:23 p.m.

    In every camera I’m familiar with (I shoot mostly Fuji), the DR modes operate by altering the ISO implementation to reduce the pre-ADC amplification by 1 or 2 stops (or the actual sensor exposure), often resulting in no “normal” analog pre-ADC amplification at all. This is how highlight headroom is increased, with the 1 or 2 stop “darker” raw files being compensated for in the jpeg processing (with a softer curve in the highlights). Unless your raw editor is compensating automatically (Lightroom and Capture One do via metadata tags), your raw files would always appear 1 or 2 stops darker at default import settings than raw files produced without DR modes (or the jpegs), despite being shot at the same ISO values.

    Edit: to clarify, I completely agree that the choice of ISO value can, and usually does, affect the RAW file, but the ISO value designation does not apply to the RAW file.

  • Members 14 posts
    April 12, 2023, 1:02 a.m.

    Even as measurement charts published by photonstophotos.com will invariably show that with an increase of iso-value input the base-iso level DR of a sensor will decrease (dual-gain induced dents included), I'm still somewhat confused over the question whether this holds true for the raw data file as well, given an "iso-invariant" sensor. If brightnesswise it doesn't go more sensitive with an iso increase, then why would/does it go less sensitive when it comes to DR-scope? The main reason why I'll try to keep a low iso-setting and apply ETTR to some feasible extent – while sticking to a DR100 stance – is to retain as much as I can of the sensor's base-iso DR-range level. Hoping that I'm not all too deceived over such prudent care.

  • Members 1737 posts
    April 12, 2023, 1:12 a.m.

    If the marks on the graph indicate normal processing (filled in circles) then gain is applied to the raw values as the ISO goes up, and you lose headroom.

    Here's an example of a camera that stops applying gain to the ISO values at a certain ISO.

    www.photonstophotos.net/Charts/PDR.htm#FujiFilm%20GFX%2050S

  • Members 457 posts
    April 12, 2023, 1:28 a.m.

    As ISO increases, the maximum possible exposure decreases, and, therefore, the max. DR decreases.

  • Members 1737 posts
    April 12, 2023, 1:31 a.m.

    But not for all cameras at all ISO settings. Eg, the GFX 50S

  • Members 457 posts
    April 12, 2023, 1:45 a.m.

    Yes. In those cases P2P will not show a decrease in DR.

  • Members 2331 posts
    April 12, 2023, 1:46 a.m.

    your understanding is the same as what i have read. but post ADC manipulation is only for expanded iso settings.

  • Members 976 posts
    April 12, 2023, 1:54 a.m.

    No, not only; and there is no such thing as "expanded iso settings" in the relevant standard.

  • Members 2331 posts
    April 12, 2023, 2:07 a.m.
    Screenshot 2023-04-12 120923.jpg

    JPG, 92.9 KB, uploaded by DonaldB on April 12, 2023.

  • Members 976 posts
    April 12, 2023, 1:10 p.m.
  • Members 1737 posts
    April 12, 2023, 2:47 p.m.

    Define "expanded ISO settings". I've seen cameras like the GFX 50S where the ISO settings where the JPEG brightness and raw file numbers are disconnected at what appear to be normal ISO settings.

  • Members 1737 posts
    April 12, 2023, 2:49 p.m.
  • Members 976 posts
    April 12, 2023, 2:57 p.m.

    I think another example would be DR400 / DR200 settings on some Fujifilm cameras.

  • Members 16 posts
    April 13, 2023, 4:26 p.m.

    Just read your camera's manual. Each manufacturer clearly describes ISO as used in their cameras in their user manuals.

  • Members 1737 posts
    April 13, 2023, 4:40 p.m.

    I have never seen the niceties of ISO implementation (dual conversion gain, programmable gain amplification, digital gain, raw developer gain, or their implications for photography) covered in a camera manufacturer's user manual.

  • April 13, 2023, 4:53 p.m.

    The problem is that the description in many manuals describes an impossibility. It cannot be correct, yet their technical authors wrote it nonetheless.

  • Members 976 posts
    April 13, 2023, 4:54 p.m.

    From a manual:
    "Sensitivity can be set higher than the default setting (ISO 200 equivalent) when taking photographs in low light conditions"
    "The default setting of ISO 200 equivalent is recommended in most circumstances. Photographs taken at other settings may include a slight amount of noise."
    That's very useful :)

  • Members 280 posts
    April 13, 2023, 5:18 p.m.

    More likely it was written by a freelance technical writer.

    Don