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A new exposure triangle for raw shooters

JimKasson
June 11, 2023
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    JimKasson
    Members 1738 posts
    June 11, 2023, 5:16 p.m. June 11, 2023, 5:16 p.m.
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    Here's a graphic that displays the light levels recordable at various ISOs in a camera with a base ISO of 100. It ignores read noise.

    image.png

    Comments?

    image.png

    PNG, 37.5 KB, uploaded by JimKasson on June 11, 2023.

    bastibe, pwilly, Hoppy and 3 other users like this.

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    finnan
    Members 322 posts
    June 11, 2023, 8:16 p.m. June 11, 2023, 8:16 p.m.
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    HAND.

    CrashpcCZ likes this.

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    JimKasson
    Members 1738 posts
    June 11, 2023, 9:46 p.m. June 11, 2023, 9:46 p.m.
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    @finnan has written:

    Seems somewhat plausible for a camera / sensor with an ~12 bit linear ADC.

    Or 13, 14, or 16 bits of precision.

    @finnan has written:

    However, I don't see how it accounts for model specific highlight headroom.

    That's a myth, measured with respect to full scale. I've only tested one camera with significant highlight nonlinearity before clipping, and that camera only did it at one ISO setting. I think the myth got started because of the different ways that camera's metering systems are set up.

    @finnan has written:

    And afaik there exist cameras / sensors with various bit depths, even dual output gain designs (e.g. Arri, Panasonic).

    As I said in the OP, I'm ignoring read noise here. And precision doesn't play a part in this graphic if the ADC precision is12 bits or more, so I'm not understanding what you're getting at here.

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    SrMi
    Members 457 posts
    June 11, 2023, 9:54 p.m. June 11, 2023, 9:54 p.m.
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    @JimKasson has written:

    That's a myth, measured with respect to full scale. I've only tested one camera with significant highlight nonlinearity before clipping, and that camera only did it at one ISO setting. I think the myth got started because of the different ways that camera's metering systems are set up

    I wonder if that myth was started by including highlight reconstruction, i.e., the camera’s behavior after clipping of at least one channel. I have observed different amount of highlight reconstruction potential with different cameras (Leica M), but have not looked into it in more details. Highlight recovery is a game of luck as one never knows whether color will be preserved or not. Nonetheless, it is very helpful when exposing incorrectly.

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    JimKasson
    Members 1738 posts
    June 11, 2023, 10:27 p.m. June 11, 2023, 10:27 p.m.
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    @SrMi has written:

    I wonder if that myth was started by including highlight reconstruction, i.e., the camera’s behavior after clipping of at least one channel.

    As I understand it, highlight reconstruction is affected in the camera design mainly by the compromise matrix, and thus the CFA. But highlight reconstruction is not performed in camera, but by the raw developer.

    SrMi likes this.

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    IliahBorg
    Members 976 posts
    June 11, 2023, 10:43 p.m. June 11, 2023, 10:43 p.m.
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    @finnan has written:

    model specific highlight headroom

    Does photo diode-specific highlight headroom make sense?

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    Deleted Removed user
    June 12, 2023, 1:29 a.m. June 12, 2023, 1:29 a.m.
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    @IliahBorg has written:
    @finnan has written:

    model specific highlight headroom

    Does photo diode-specific highlight headroom make sense?

    Maybe ...

    kronometric.org/phot/sensor/diodeSat.gif

    JohnMoyer likes this.

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    IliahBorg
    Members 976 posts
    June 12, 2023, 2:24 a.m. June 12, 2023, 2:24 a.m.
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    @xpatUSA has written:
    @IliahBorg has written:
    @finnan has written:

    model specific highlight headroom

    Does photo diode-specific highlight headroom make sense?

    Maybe ...

    kronometric.org/phot/sensor/diodeSat.gif

    Shoulder is what I see ;)
    Even more interesting in photo-voltaic mode (used in some technical sensor applications, I use one of those to shoot welding).

    JohnMoyer likes this.

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    SrMi
    Members 457 posts
    June 12, 2023, 5:22 a.m. June 12, 2023, 5:22 a.m.
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    @JimKasson has written:
    @SrMi has written:

    I wonder if that myth was started by including highlight reconstruction, i.e., the camera’s behavior after clipping of at least one channel.

    As I understand it, highlight reconstruction is affected in the camera design mainly by the compromise matrix, and thus the CFA. But highlight reconstruction is not performed in camera, but by the raw developer.

    Any highlight headroom comparison and analysis that I have seen, evaluated how clipped raw files are handled by raw developer :(.

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    finnan
    Members 322 posts
    June 12, 2023, 6:19 a.m. June 12, 2023, 6:19 a.m.
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    HAND.

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    SrMi
    Members 457 posts
    June 12, 2023, 6:59 a.m. June 12, 2023, 6:59 a.m.
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    @finnan has written:

    Sorry, I just don't buy that.

    Can you elaborate? Jim's graphic is not related to DR, as I understand it.

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    finnan
    Members 322 posts
    June 12, 2023, 7:26 a.m. June 12, 2023, 7:26 a.m.
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    HAND.

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    JimKasson
    Members 1738 posts
    June 12, 2023, 3:45 p.m. June 12, 2023, 3:45 p.m.
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    @xpatUSA has written:
    @IliahBorg has written:
    @finnan has written:

    model specific highlight headroom

    Does photo diode-specific highlight headroom make sense?

    Maybe ...

    kronometric.org/phot/sensor/diodeSat.gif

    With one exception at one ISO setting, all the cameras I've tested are designed so that the ADC clips before the curve above bends over far enough to be photographically useful.

    IliahBorg and SrMi like this.

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    JimKasson
    Members 1738 posts
    June 12, 2023, 3:48 p.m. June 12, 2023, 3:48 p.m.
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    @finnan has written:
    @SrMi has written:
    @finnan has written:

    Sorry, I just don't buy that.

    Can you elaborate? Jim's graphic is not related to DR, as I understand it.

    Maybe I simple have no idea what Jim refers to when he says "light levels recordable at various ISOs" in the OP.
    Not related to DR? D'oh!

    In order to relate the graphic to DR, I'd have to bring in read noise and photon noise, and also pick a SNR threshold. That would make it camera specific. I didn't want to do that. DR is full scale over mean at some threshold SNR, so you can't read DR off the graphic. What the graphic does show is the effect of ISO setting on full scale with full scale measured in lux-seconds of exposure.

    For camera-specific DR vs ISO curves, see Bill Claff's PDR charts.

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    IliahBorg
    Members 976 posts
    June 12, 2023, 3:59 p.m. June 12, 2023, 3:59 p.m.
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    @JimKasson has written:

    With one exception at one ISO setting, all the cameras I've tested are designed so that the ADC clips before the curve above bends over far enough to be photographically useful.

    Same here.

    JimKasson likes this.

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    finnan
    Members 322 posts
    June 12, 2023, 6:23 p.m. June 12, 2023, 6:23 p.m.
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    HAND.

    JohnMoyer likes this.

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    IliahBorg
    Members 976 posts
    June 12, 2023, 6:38 p.m. June 12, 2023, 6:38 p.m.
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    @finnan has written:

    Why stop at 11?

    "above arbitrary base".

    JimKasson likes this.

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    finnan
    Members 322 posts
    June 12, 2023, 9:12 p.m. June 12, 2023, 9:12 p.m.
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    HAND.

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