Advanced Techniques - Adobe Photoshop Elements 11 for Photographers - page 217

24-bit color photograph (8 bits per channel)

256 levels of red

= a combined
total of 16.7
million colors

256 levels of green

256 levels of blue

48-bit color photograph (16 bits per channel)

65,536 levels of red

= a combined
total of
281,474,976
million colors

65,536 levels of green

Comparing Bit Depth:
The higher the bit depth
of an image the more lev-
els of tone and number
of colors it can display.

65,536 levels of blue

Here are the main advantages in a nutshell:

1 Capturing images in high-bit mode provides a larger number of colors for your camera or
scanner to construct your image. This in turn leads to better color and tone in the digital
version of the continuous tone original.
2 Global editing and enhancement changes made to a high-bit file will always yield a better
quality result than when the same changes are applied to a low-bit image.
3 Major enhancement of the shadow and highlight areas in a high-bit image is less likely to
produce posterized tones than if the same actions were applied to a low-bit version.
4 More gradual changes and subtle variations are possible when adjusting the tones of a
high-bit photograph, using tools like Levels, than is possible with low-bit images.

1 2

Redistributing the tones on an 8 bits per channel file (2) can lead to loss of levels of gray (white spikes) and
noticeable 'banding' in the image. 16 bits per channel files (1), by contrast, maintain their appearance of
continuous tone even after quite drastic editing and enhancement actions.