Bit depth refers to the number of bits used to construct the color/tone of each pixel. For color, 8-bit is the same as 24-bit as there are 8 bits for each of the three color channels: red, green, and blue (RGB). 16-bit is the same as 48-bit since there are 16 bits per channel.
Black and White:
Bitonal (1 bit) images: Each pixel can be black or white
Grayscale (8 bit) images: Each pixel can be one of 256 shades of gray
RGB: red, green, blue – the colors of light used by monitors, scanners, projectors, cameras, etc., to create all other colors
CMYK: cyan, magenta, yellow, black – the colors used by printing presses, and many copiers and desktop printers, to create all other colors
Copies of the master file that have been modified and saved.
The highest quality digital image. Any modifications should be made to a duplicate of the file, e.g., a derivative file.
A megapixel is one million pixels.
The smallest unit of information in an image.
Resolution is the density of pixels in a given area. Digitized images are made up of a fixed grid of pixels. Therefore a 100 pixels-per-inch (PPI) image will have a grid of 10 pixels across and 10 pixels down in every inch; a 400 ppi image will have a grid of 20 pixels across and 20 pixels down in each inch.
DPI, PPI, and SPI are often used interchangeably which is incorrect and can be confusing:
PPI: pixels per inch — describes the digital resolution of an image
DPI: dots per inch — describes the output resolution of a given printer
SPI: samples per inch — describes the number of samples per inch a scanner takes of an image
LPI: lines per inch — relates to printing method and is very different from the other terms