|
|
 |
|
|
|
|
|
RGB can express 16.7
million colors.
Tones are the numbers that express the concentrations
of the various colors. Four tones would mean color concentrations of 0%, 25%, 50%, and
100%, for example. Hence, the more tones, the richer the hues and separations, and the
smoother the gradations that can be depicted.
Digital photos typically can depict 256 tones each
of red, green, and blue, making for a total of 256
x 256 x 256 = 16.7
million colors (tones) that can be expressed this way.
Images capable of depicting the 256 respective tones of each color are referred to as being 24-bit RGB because 2^24
is 16, 777, 216 (or roughly 16.7 million). |
|
 |
|
|
There are other image tones besides these as well, such as grayscale,
which has 256 shades of gray, and is used for black-and-white images, and index colors, of which there
are also 256. As they have so few gradations compared with RGB, however, they do not transition nearly
as smoothly, and are thus unsuited for photographic use. |
|
|
|
|
|
|
RGB |
Grayscale |
Index color |
|
 |
 |
 |
|
Using 48-bit mode to express even finer
colors.
More and more recent digital cameras and color scanners have added 36-bit and even 48-bit color to their capabilities,
consisting of 12 and 16 bits each of RGB, respectively.
Photoshop reads these images 48-bit mode, which obviously has far more tones than 24-bit RGB
and, thus, can express even finer colors. For level or tone curve retouching, this mode also has fewer problems with image
quality or tone problems.
Using 48-bit color is useful for preserving delicate colors and gradations. |
|
|
|
Photo Retouch
