Modes (Color and Image)

Image Mode
Refers to Bitmap, Grayscale, Duotone, Indexed Color, RGB Color (red, green, blue), CMYK Color (cyan, magenta, yellow, black), Lab Color, and Multichannel. These are the various modes that images can be brought into and displayed in Photoshop. Each has special characteristics for certain applications or uses.

RGB (recommended)
Red, Green, Blue. RGB mode is the recommended working mode for images in Photoshop. It allows you to apply layers, filters, and non-constrained color palettes. Working in RGB mode also allows you to save the file as a .jpg and .gif along with several other file extensions.

Black, white, and gray mode. This mode will allow you to use layers and certain filters. Working in this mode also allows you to save the file in .jpg and .gif along with several other file extensions.

Indexed Color
The image mode is constrained to a color palette of 256 colors or less. In this mode you cannot add layers, apply filters or add colors that are not already used in the image. You cannot use most of the editing tools. This mode allows the file to be saved as a .gif, .psd or .pdf (Photoshop formats), or .png. Saving as other types of files may cause a distorted image.


Additional Terms

Aliased vs. Anti-Aliased options
Photoshop allows you to create anti-aliased text, which results in smooth edges of letters. Anti-aliased edges on a selection or text gives a smooth-edged appearance. Blending the edge pixels with the surrounding pixels produces this effect. If aliasing is turned on (aliased), a jagged stair-stepped appearance results.

Squares (pixels) of color placed in uniform rows to form an image. You can save as a Bitmap file (.bmp or .btmp) and several other file types.

Canvas Size
The overall dimension of the image. In Image and Canvas sizes you can increase or decrease numerically the dimensions of the image. Any additional area you add to your canvas will appear as a color border around the original canvas. This border will appear in the same color as your background color unless you choose a different color before you adjust the canvas size.

Color bands
Distinct bands of color resulting from the reduction of the color palette of an image.

Dots per inch/pixels per inch. These are resolution measurements used by scanners, printers and Photoshop. The resolution of computer monitors is 72 dpi/ppi. Gif and jpg images should be adjusted to this resolution for final saving and display.

Applies color or a percentage of color to a selection.

Special effects that are applied to all areas, selected areas, or layers of the image. You can choose from a variety of effects, from adding artistic rendering to sharpening and blurring images.

Uses the tolerance specified in the Magic Wand Options palette to select pixels adjacent to the pixel selected.

Image Size
The overall size of an image in print size. Print size can be determined by percent, inches, centimeters, points, or picas. Using Image size, you can choose measurement type and adjust dimensions and resolution.
NOTE: Use caution when increasing the resolution or actual dimension of the image: it may result in a less sharp image.

Layers act as separate films, much like transparency sheets. Each layer contains objects which, when layered together, create a composite image. Each layer contains its own discrete contents.

The transparency that you affix to a tool, layer, or color. The lower the percentage is, the more transparent the effect; the higher the percentage, the more opaque the effect.

Paint Bucket
Applies color or a percentage of color to an area within the tolerance setting of the pixel addressed. This differs from Fill because it affects those pixels within the tolerance, whereas Fill affects all of the pixels within the selection.

A grid square that consists of one color. In combination with all of the other pixels, it makes up the image that we see on screen. All Photoshop images are bitmapped into pixels.

Selects like color pixels that are already selected throughout the image.

A border applied with the foreground color to selected portions of an image. Stroke is measured in pixels and can be placed on the outside, center, or inside of the selection.

A value range from 0-255. The lower the number entered the more similar the color that will be selected. The higher the value the broader the color range that will be selected.