Colorizing b/w photos

Discussion in 'Digital Cameras' started by Piotrne, Feb 11, 2014.

  1. Piotrne

    Piotrne Guest


    the problem of colorizing black-and-white photos probably
    has been solved a long time ago (judging from the number
    of colored films), but I could not find a meaningful tool
    for this purpose in GIMP. Maybe someone already colorized
    a b/w picture? Of course I found a lot of tutorials how
    you can do that both in GIMP and Photoshop. But proposed
    methods seem to me to be inappropriate. In any case,
    it would be difficult to colorize a video this way.
    I'm using GIMP, so all examples and question apply to GIMP.

    There are two basic ideas to colorize a b/w photo:

    - Select (manually) an area in the photo, which should be
    assigned a given color. Select the tool "color curves"
    or "colorize" and set the desired color. Repeat for other
    areas of the image and different colors.

    - Create a new layer for applying colors. Set it’s mode (in GIMP)
    to "multiply" or "overlay". Then paint colors with standard tools.

    The first method is suitable only for very simple cases. It's a bit
    like a cutout of a colored foil applied to the photo and would take
    a lot of time in case of e.g. a fine, colorful pattern on clothing.

    I tried the second method with "overlay" mode. This is the only mode
    that gives reasonable results, although it is impossible to directly
    obtain the maximum saturation of a color. I have to increase
    the saturation of the ready image. So, this is not what I expect
    from the "color layer".

    I want to have one layer with luminosity (the black-and-white photo)
    and another layer for colors. And for example, for a red object
    illuminated in different ways (and visible on the b/w photo),
    I would like to get following dependencies:

    Gray level on the b/w photo + color on the second layer ---> resulting color
    black + anything ---> black
    gray (R128,G128,B128) + red (R255,G255,B255) ---> red (R255,G255,B255)
    white + anything ---> white

    The "overlay" mode gives almost this behavior, after saturating the image.
    Other, more obvious modes don’t give such control. For example, in the
    "value" mode (upper layer: b/w photo in "value" mode, bottom layer:
    colors in "normal" mode), the combination of white + red gives red. This is not
    a normal situation, because e.g. bright reflections on a red object (visible
    as white spots on the b/w photo), should remain white, and not red.

    Anyway, even in this mode it is a bit hard to obtain realistic effects.
    Is it possible to decompose a color photo into such two layers as described
    above? Just to check, how a perfect colorizing should look like.

    Or maybe there is another color model (similar to HSV or HSL) that would
    make colorizing easier? One component (channel) should be brightness
    (V), while the other two components should be something easy to draw
    by hand, for example for the whole area of a human face.
    I have tried to use the HSV model. Unfortunately, without success.
    The channel V looks more or less like a black-and-white photo. The channel H
    has quite similar values for the whole face, but the channel S resembles
    a negative b/w photo, which is rather impossible to reproduce manually.

    Piotrne, Feb 11, 2014
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  2. Piotrne

    Guest Guest

    if you're using the gimp, you're going to have a difficult time because
    it lacks features that are *very* helpful for colourizing, namely
    adjustment layers.

    it's not impossible with the gimp but it's a lot more work than it
    needs to be.
    the best way to do this is with multiple coloured layers for different
    parts of the photo, masked appropriately and with whatever blend mode
    and opacity works best for the effect you want to achieve. there is no
    one blend mode that will work for everything.
    Guest, Feb 11, 2014
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  3. Piotrne

    J. Clarke Guest

    And you have successfully colorized black-and-white photos by sliding
    the hue slider?
    J. Clarke, Feb 12, 2014
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