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Thread: interesting new question

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    Senior Member
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    Nov 2005
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    Wisconsin
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    Name
    S. Gru.
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    SgWRX

    United States

    Default interesting new question

    so lately, i've found my custom bitmaps created in photoshop often appear different when i render it inside max. the image i create is typically srgb and typically grabbed from a manufacturers website (carpet samples or wood samples).

    i've been getting a lot of red-shift. for example, the brown wood from the manufacturers website (usually un-tagged) in photoshop (assigned my monitor profile, then converted to srgb) looks similar to what i see on screen in the web browser (firefox with CM turned on).

    i can usually correct by either huge desaturation of the wood in photoshop, or using the color correction map in 3ds max, with the image as a sub map.

    now, recently it occurred to me, that a photo from a website has a low color range (gamut) to it and it was photographed under a specific intensity and color of light with a specific white balance and exposure value taking that into 3ds max and then adding a light in the scene, changes those colors.

    i recently did a quick test where i took a sample of a parquet floor into photoshop and simply reduced the "brightness" via a brightness/contrast adjustment layer and rendered it with default photometric light and exposure control. the result was a rendered bitmap that had a more similar color/brightness rendition to what i see in my web browser with that same image and in photoshop.

    in max, by adding illumination, you are cranking up the values of the colors in the bitmap which might be similar to "over exposure".

    what i haven't tried yet, but will as soon as time permits, is to photograph a physical sample of some carpet we have, then try to match the exposure and lighting values in max to the conditions of the photograpah using a grey card to set white balance.

    i also found that when doing 32bit frame render (hdr) and then adjusting in photoshop, the bitmaps in the scene do not adjust in exposure the way a&d materials with only diffuse color setting. for example a light grey wall remains faithfully smooth throughout the exposure adjustment from black to white whereas bitmaps get all blocky and terrible. this is to be expected i suppose because the bitmap was low dynamic range to begin with.

    edit: sorry, i guess the question is, how do you take an ldr image and get it to match in color/brightness in a render (hdr or ldr).

    or at least predictable. i think you almost have to compensate in bitmap's brightness/exposure so that no pixel is "blown out" when add light to it inside 3ds max.
    Last edited by SgWRX; September 13th, 2015 at 12:27 PM.

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