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Finding and Using Good Images

Online Guides for Image Sizing, Format and Use

Digital Image Vocabulary

Pixel - a "picture element" that represent a brightness sample within the color model (see more below) of the image. Pixels are often referred to as the smallest element of a digital image, though this is not a fully accurate description, and are small squares within the image, which are arranged on a grid formation.

Resolution - Input resolution is measured in pixels per inch (ppi), the density of pixels of the image. This is not the number of pixels per square inch. A 100x100 ppi image printed at 1 inch would have 100 pixels per inch. If you printed that same image in a larger format the ppi would go down, and thus your resolution would be lower. The same image printed in a smaller format would have a higher ppi, therefore a higher resolution. Output resolution is measured in dots per inch (dpi). This is a measure of how many dots the printer can printer per inch (or monitor can display) horizontally and vertically.

Dimensions - The dimensions of an image are the physical width and height of the image. The pixel dimension is the number pixels across the long and short sides of the image.

Color/Bit Depth - Color, or bit, depth (bits per pixel, bpp) is the number of bits to express color per pixel. A larger bpp indicates a bigger range of colors that can be used for each pixel, which increases the color range represented in an image.

Color Model - Color models use a subset of colors that are used in combination to display an array of colors. Red-Green-Blue (RGB), Grayscale and Cyan-magenta-yellow-black (CMYK) are common digital image color models. The color space is the color created by these color models.

File Size - The file size of an image is the total number of bits of disk space the image occupies.