Basic Concepts of Digital Imaging Chapter Two Basic Concepts of Digital Imaging

Resolution Given a digital image of a certain size, the more pixels it has, the higher its resolution. pixel = picture element 1 mega pixels = 1 million pixels One measure of the visual detail contained in a digital image In general, the more mega pixels a digital image has, the more detail it contain.

Example (640x480=307,200 pixels)

Example 5610x3627 = 20 mega pixels

Bit Depth 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 example, a pixel with a bit depth of 1 has two possible values: black and white. A pixel with a bit depth of 8 has 28, or 256, possible values.

Bit Depth 8-bit 4-bit 1-bit

8 Bit vs. 16 Bit 8 bit gives 256 tonal values It is likely that your digital cameras record images using 8-bit in the JPEG format. More expensive digital cameras allow you to save images using 12/14/16-bit in the RAW file format. (example)

Color Modes Grayscale (Black and white) RGB (Red, Green, Blue) Most common for digital photography CMYK (Cyan, Magenta, Yellow, blacK) Most common for (digital) printing Lab Reference color space for conversion

RGB vs. CMYK

File Formats JPEG TIFF RAW Convenient, compression, lossy Lossless, large files RAW Proprietary (e.g. Canon’s CRW, Nikon’s NEF) Large files High bit-depth (e.g. 14-bit, 3 channels)

JPEG Quality