To begin to understand Photoshop s potentials, one must first understand the language of its file types. File types are all about compression. Depending on what purpose the image serves, how many colors it contains, the image quality (resolution), the number of layers, and what viewing/printing size you want the image to be will determine what file type would provide the highest quality image while taking the least amount of space (usually in terms of megabytes). ...

To begin working on an image, you can either start with a blank page or open/import a file from another location.

Starting with a blank page is the most important place to begin creating an image because it involves more than just working from scratch, but also comes in use when merging other images together. This involves copy, cut, and paste techniques that will be discussed in more detail later in the tutorial.

Once you have scrolled up to the menu bar and selected Newâ ¦ in the File option, you have a list of option to create a new file. Most of the options are fairly self-explanatory. The size of the file can either be adjusted by the â Preset Sizesâ options or by self adjusting the width and height in various units (inches, pixels, etc.). The mode refers to the type of colors you want to have available for the image, such as RGB (Red, Green, Blue; the most widely used) and Grayscale. CMYK (Cyan, Magenta, Yellow, Black) also has a wide variety of colors, but not as many as RGB. CMYK was once preferred when printers were limited to the shades of color more closely imitated by CMYK than by RGB. Now, new developments in technology have made the colors of RGB recognized by printing systems.

Source: www.ulv.edu