Know Your Color Spaces
Each color space has a personality. Some are rough characters whose reactions are hard to predict, others are refined, and take more prodding, all are are capable of giving you excellent results, providing you know what each is best for. The following table summarizes some of the strengths and weaknesses of each color space. Note: more dots = better.
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Color
Space
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Adjust
Shadow
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Adjust
Highlight
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Adjust
Neutral
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Adjust
Overall Brightness
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Adjust
Saturation
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Coarse
or Fine Adjustment
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RGB
|
 |
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|
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--- |
Coarse
|
|
wgCMYK
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|
|
|
|
|
Fine
|
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Lab
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|
|
|
|
|
Coarse
|
|
HSB
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|
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--- | |
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In-Between
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Of the four color spaces supported by Curvemeister, RGB is the only
purely electronic-based capture and display space. It is probably the most popular
color space among the growing group of photographers and graphic artists who
are not directly involved in putting ink to page. From a color correction standpoint,
although RGB does not excel in any particular adjustment, because brightness
and color information are mixed together, it is still a good all-around correction
space.
RGB does best at fixing mixed lighting situations, where a color cast
is associated with a change in brightness. RGB is also a good source
of vivid masks.
Curvemeister hopes to tilt the balance away from RGB and toward some of the
other color spaces.
Wg-CMYK (wide gamut CMYK) is a special CMYK color space, available
only in Curvemeister, that is mathematically equivalent to RGB. So it
is a close cousin of RGB, with an additional K, or black, color channel. Wg-CMYK
is a new color space that offers the advantages of CMYK color correction, and
avoids of the color range issues associated with real CMYK.
Wg-CMYK provides direct control over shadows and other dark objects, and
for this purpose it is the best of all the color spaces supported by Curvemeister.
Because of this separation of shadow and color, wg-CMYK also provides
good control of subtle color differences. By adjusting the black separation,
it is possible to adjust the color and saturation of colored objects without
altering existing neutrals.
Wg-CMYK is best for images with dark objects, or images with many contrasting
colors. The K channel, is a good source of masks because it may be controlled
via black generation.
Lab provides almost perfect separation of brightness and color information.
This allows fine control over highlight and shadow, plus the ability to adjust
very large color casts and dramatically increase saturation. Because it occupies
such a large color gamut, it is an excellent color space for correcting large
color casts, and neutralizing or otherwise altering the shade of a single color.
Lab is a poor color space for subtle color adjustments, or for neutralizing
two or more shades of color. Lab excels at distinguishing shades of green
foliage.
The a and b channels of Lab are good sources of masks for separating
uniquely colored objects because they depend on hue only, and will therefore
trace a true outline of an object in variable lighting.
HSB, like Lab, also separates brightness and color
information, but in a different way. It is a good space for increasing saturation,
and for correcting certain types of large color casts where the intensity of
the color is correct, but the particular color is wrong.. In most cases, for
most images, HSB is a poor choice for adjusting neutrals, since all colors
will de-saturated by the same amount.
The H channel of HSB can be a good source of masks that are based on
color, provided the lighting is adequate, but Lab is generally better
for this purpose.
