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Scene luminance has nothing to do with exposure.

DonaldB
June 16, 2023
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    DonaldB
    Members 2434 posts
    June 16, 2023, 2:48 a.m. June 16, 2023, 2:48 a.m.
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    Open for Discussion.

    My comment . the camera is taking the exposure, the scene is what it is.

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    IanSForsyth
    Members 216 posts
    June 16, 2023, 3:32 a.m. June 16, 2023, 3:32 a.m.
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    I tried to take a photograph with no scene luminance
    photos.smugmug.com/Temp/Temp/i-FxzTPhm/0/e3cfed06/M/sdfdf-M.jpg
    And this is what I got
    So I would think that it is

    TonyBeach, CrashpcCZ, TimRichards and 5 other users like this.

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    JACS
    Members 878 posts
    June 16, 2023, 3:45 a.m. June 16, 2023, 3:45 a.m.
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    [deleted]

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    IanSForsyth
    Members 216 posts
    June 16, 2023, 4:07 a.m. June 16, 2023, 4:07 a.m.
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    If there is no rain and you stand outside have you been exposed to rain? Would you not need to have some kind of exposure to rain to get exposed to rain?

    If a guy runs up to me wearing a trench coat and flashes me but he is wearing normal clothing underneath the trench coat have I been exposed to nudity?
    Would there not be the need to have exposure to nudity to say I was exposed to nudity?

    CrashpcCZ likes this.

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    SrMi
    Members 457 posts
    June 16, 2023, 4:13 a.m. June 16, 2023, 4:13 a.m.
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    Exposure determines how much light hits the sensor. That depends on shutter speed, aperture, and scene light.

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    Porky
    Members 128 posts
    June 16, 2023, 4:17 a.m. June 16, 2023, 4:17 a.m.
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    It does if you want your photo to look like your subject! :)

    CrashpcCZ likes this.

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    SrMi
    Members 457 posts
    June 16, 2023, 4:37 a.m. June 16, 2023, 4:37 a.m.
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    @Porky has written:

    It does if you want your photo to look like your subject! :)

    That is not the role of exposure. E.g., the lightness (ISO) and the colors (WB) are not part of exposure.

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    IanSForsyth
    Members 216 posts
    June 16, 2023, 4:46 a.m. June 16, 2023, 4:46 a.m.
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    @SrMi has written:

    That is not the role of exposure. E.g., the lightness (ISO) and the colors (WB) are not part of exposure.

    What happens if I pre WB the light with light modifiers to produce a uniform WB across different light sources in the scene?

    If I am modifying my illuminate to cast a different WB differently across my FOV or if I am introducing colored light to a backdrop then WB and color can part of the exposure

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    GreatBustard
    Members 755 posts
    June 16, 2023, 4:52 a.m. June 16, 2023, 4:52 a.m.
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    @DonaldB has written:

    Open for Discussion.

    My comment . the camera is taking the exposure, the scene is what it is.

    What does "taking the exposure" mean, though? "Recording the exposure"? If so, then, sure, your camera is "taking the exposure", but the exposure it is taking is a function of the scene luminance, the f-number, and the exposure time. And, yes, you or your camera can alter the f-number and/or exposure time to account for different scene luminances to get the same exposure, but this doesn't change the fact that scene luminance is a factor in the exposure.

    Deleted likes this.

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    PeteW
    Members 184 posts
    June 16, 2023, 4:54 a.m. June 16, 2023, 4:54 a.m.
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    @DonaldB has written:

    Open for Discussion.

    My comment . the camera is taking the exposure, the scene is what it is.

    Well played, Don. 😉

    I suspect that this thread already has a space reserved for it in the Dumpster. It's only waiting for Danno to contribute before the mods send it south.

    Danny, JACS, CrashpcCZ and 1 other user like this.

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    DonaldB
    Members 2434 posts
    June 16, 2023, 6:26 a.m. June 16, 2023, 6:26 a.m.
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    @IanSForsyth has written:

    I tried to take a photograph with no scene luminance
    photos.smugmug.com/Temp/Temp/i-FxzTPhm/0/e3cfed06/M/sdfdf-M.jpg
    And this is what I got
    So I would think that it is

    same i took an image at 12,000 sec at f32 iso 50 and got the same 🙄

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    Danny
    Members 435 posts
    June 16, 2023, 6:34 a.m. June 16, 2023, 6:34 a.m.
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    Yeah Don, I got exactly same as well at 50 seconds at F/1.8 with ISO 22,000. Then I took the lens cap off mate 😉

    JimStirling likes this.

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    DonaldB
    Members 2434 posts
    June 16, 2023, 6:44 a.m. June 16, 2023, 6:44 a.m.
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    @GreatBustard has written:

    but the exposure it is taking is a function of the scene luminance

    then the exposure it is taking is a function of iso also 😊

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    DonaldB
    Members 2434 posts
    June 16, 2023, 6:46 a.m. June 16, 2023, 6:46 a.m.
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    @Danny has written:

    Yeah Don, I got exactly same as well at 50 seconds at F/1.8 with ISO 22,000. Then I took the lens cap off mate 😉

    thats right, you took a great exposure of a black lens cap. 😁

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    DonaldB
    Members 2434 posts
    June 16, 2023, 6:47 a.m. June 16, 2023, 6:47 a.m.
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    @PeteW has written:
    @DonaldB has written:

    Open for Discussion.

    My comment . the camera is taking the exposure, the scene is what it is.

    Well played, Don. 😉

    I suspect that this thread already has a space reserved for it in the Dumpster. It's only waiting for Danno to contribute before the mods send it south.

    we already know Dunnos answer as we have read it in every post. 😏

    DannoLeftForums likes this.

    favorite 1

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    DonaldB
    Members 2434 posts
    June 16, 2023, 6:55 a.m. June 16, 2023, 6:55 a.m.
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    @GreatBustard has written:

    but this doesn't change the fact that scene luminance is a factor in the exposure.

    its not a factor of exposure and in fact less so than ISO, the scene is the scene period. we set and take the exposure to how bright we want the image.

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    GreatBustard
    Members 755 posts
    June 16, 2023, 6:59 a.m. June 16, 2023, 6:59 a.m.
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    @DonaldB has written:
    @GreatBustard has written:

    but the exposure it is taking is a function of the scene luminance

    then the exposure it is taking is a function of iso also 😊

    Yes, you can use the ISO control on the camera to indirectly change the exposure by making the camera choose a different f-number, exposure time, and/or flash power, depending on the mode you're using, and it is those changes that alter the exposure. But the ISO setting, in and of itself, is not an element of exposure, anymore than your fingers or thumb, which you use to change the ISO setting, are part of exposure.

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    DonaldB
    Members 2434 posts
    June 16, 2023, 7 a.m. June 16, 2023, 7 a.m.
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    @SrMi has written:

    Exposure determines how much light hits the sensor. That depends on shutter speed, aperture, and scene light.

    Exposure doesnt include scene light. exposure is shutter, and t stop.

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