Highest Quality Capture: Workflow Phase I - Black and White in Photoshop CS4 and Photoshop Lightroom - page 34

III. Bit Depth: The Advantage of
High Bit Capture

Bit depth, also called pixel depth or color depth, measures how much color
information is available to display or print each pixel in an image. Greater bit
depth (more bits of information per pixel) means more available colors and
more accurate color representation in the digital image.

For the technically curious, the explanation of bit depth requires some
complicated math. For the less technically adept, however, all you really
need to know is that more bits are more better! Working in high bit provides
exponentially more information within the image i le.
Fundamentally speaking, a pixel with a bit depth of 1 has two possible values:
black and white, it can be 1 or 0, on or of .

2-bit image

Digital i les can be:
1. Low bit: (8-bit) Most of the digital world operates with 8-bit images. This
includes inkjet printers, most monitors and all JPEG i les.

A pixel with a bit depth of 8 2 8 has 256 possible values.

2. High bit: (16, 24, 32 or 48 Bit) A high-bit image in contrast can have
65,536 (2 24 ) levels of information, which is signii cantly more than the
256 levels that an 8-bit image contains. The signii cantly greater amount of
information available in the image i le makes a dramatic dif erence when
moving pixels and image data in the editing process. Only raw capture,
and high bit scanning can give you the advantage of high-bit images and
Photoshop can now process up to 32-bit.

8-bit image with same editing results in
banding and posterization

Less destructive editing means less spikes and gaps in the histograms, and
smoother gradations cause less banding and posterization. (See “So what
is a histogram?,” page 42 for more information.)

High-bit image with some editing contains
more image data