Apple Aperture Digital Photography Fundamentals - Manual (Page 40)

40 Chapter 3 Understanding Resolution
The following example illustrates how increasing the bit depth of a pixel increases the
number of color values it can represent. Increasing the bit depth by 1 bit doubles the
number of possible color values.
How Resolution Measurement Changes
from Device to Device
As you now understand, resolution in itself isn’t complicated; it simply measures how
much detail an image can hold. However, as resolution is described for different digital
devices—cameras, displays, and printers—the different units of measurement can be
confusing. A camera’s resolution is calculated by the number of megapixels (millions of
pixels) its digital image sensor is capable of capturing. A display’s resolution is expressed
in pixels per inch (ppi) or as a maximum dimension, such as 1920 x 1280 pixels. A printer’s
maximum resolution is expressed in dots per inch (dpi)—the number of dots it can place
within a square inch of paper. These changing units make it hard to keep track of the
resolution of your digital image as it moves from one device to another. Not only do the
units of measurement change, but the numerical values change as well.
1-bit color channel
2 possible values
2-bit color channel
4 possible values
4-bit color channel
16 possible values
8-bit color channel
256 possible values
8-megapixel
camera
3500 x 2300
pixel image
1400 dpi
printer
300 dpi print at
11.66" x 7.66"