Alpha channel

Channel palette

A channel beyond the core color channels, used almost exclusively to hold masks.

Anchor point

Paths in the image window

A spot in the magnetic lasso or path outline that marks a location at which the outline arcs or changes direction.

Antialiasing

Options bar

A slight softening effect applied most commonly to selection outlines to simulate smooth transitions.

Aspect ratio

Image > Image size menu, Image > Canvas size menu

The relationship between the width and the height of an image.

Auto Color

Image > Adjustments menu

A command which both corrects and neutralizes the shadows, highlights, and midtones in an image, making it the most useful of Photoshop’s automatic levels-correction functions.

Auto Contrast

Image > Adjustments menu

A command which automatically corrects the shadows and highlights of an image but leaves the color balance unchanged.

Auto Levels

Image > Adjustments menu

A command which automatically corrects the shadows and highlights of each color channel independently. As a result, it often shifts the color balance.

Burn Tool

Toolbox

A tool that darkens portions of an image as you paint.

Calculations

Image menu

This command lets you blend two channels to form a new alpha channel that will eventually serve as a mask.

Canvas

Image window, Image > Canvas size menu

The boundaries of an image, as measured independently of the contents of the image itself.

Clone source

Clone source palette

A palette that lets you scale, rotate, and even flip the source image for a healing/clone tool.

Color Channel

Channels palette, other locations

An independent grayscale image that Photoshop colorizes and mixes with other images to produce a full-color composite.

Color Range

Select menu

This command lets you adjust the range of colors you want to select and see the results dynamically.

Contrast

various

A distinct difference between two brightness levels or two colors.

Control handle

Paths in the image window

This special kind of lever tugs at the line segment in a path outline, bending it to form a fluid curve.

Crop tool

Toolbox

A tool which allows you to cut away the extraneous portions of an image to focus the viewer's attention on the subject of the photo.

Curves

Image > Adjustments menu

A command that lets you pinpoint a specific color in an image and make it lighter or darker. It is best suited to reducing contrast.

Dodge Tool

Toolbox

A tool that lightens portions of an image as you paint.

Downsampling

Image > Image size menu, transform command

To change the physical dimensions of an image by reducing the number of pixels.

Duotone

Image > Mode menu

A colorized monochrome image which is rendered using two colors.

Edge artifacts

Image window

Harsh transitions along the edge of a layer.

Extract

Filter menu

This command erases the pixels outside an image element and leeches the fringe coloring conveyed by the original background.

Gang scanning

File > Automate menu

A quick method of capturing several images with a flatbed scanner to a single file and then sorting them out using the Crop and Straighten command.

Gradient Map

Image > Adjustments menu

The best tool for colorizing a grayscale image, because it permits you to select three or more colors as well as modify luminosity values.

Highlights, Shadows, and Midtones

Image > Adjustments menu

The three brightness ranges that you can edit independently using the Levels or Curves commands.

Histogram

Levels dialog box, Histogram palette

A bar graph representation of all brightness values and their distribution in an image.

Hue

various

An ingredient of color: the color name, from red to magenta

Interpolation

Image > Image size menu, transform command

The process of throwing away pixels and making up new ones by averaging the existing pixels in an image.

Jitter

Brush palette

A series of percentage values that permit one or more attributes to vary randomly over the course of a brushstroke.

Levels

Image > Adjustments menu

The best command for manually adjusting the brightness and increasing the contrast of an image.

Lock transparency

Layers palette

An option that limits your edits to the existing opaque pixels in a layer.

Magic wand

Toolbox

Click with this tool to select regions of color inside an image.

Masking

various

Method for creating a selection outline as an alpha channel, which you can then edit and save like any other image.

Match Color

Image > Adjustments menu

This command permits you to bring the colors in one image or layer into agreement with those in another.

Move tool

Toolbox

A tool which permits you to move selected pixels, even between images.

Origin point

Transform command

The center of rotation or other transformation.

Patch tool

Toolbox

A tool which allows you to heal a selected area, whether the selection was created with this tool or some other selection function.

Pen tool

Toolbox

A tool which lets you draw free-hand outlines one segment at a time.

Polygonal lasso

Toolbox

A tool which allows you to select free-form, straight-sided areas in an image.

Print resolution

Image > Image size menu

The number of pixels that will print within a linear inch or millimeter of page space.

Quick mask mode

Toolbox

This feature lets you press the Q key to view and modify the selection outline as a rubylith overlay.

RGB

various

Red, Green and Blue: The three primary colors of light, which mix together to form a full-color image.

Ruler tool

Toolbox

A tool which allows you to straighten a photo by dragging along an edge that should be exactly horizontal or vertical.

Saturation

various

An ingredient of color: the purity (or intensity), from gray to vivid.

Shield

Crop command: options bar

The translucent film of color that covers portions of an image that will be deleted after you apply the crop tool.

Snapshot

History palette

A special kind of state in the History palette that remains available well after 20 operations.

Source point

Image window

The spot from which a healing tool samples information when repairing a flaw in an image.

Sponge tool

Toolbox

A tool which decreases or increases the saturation of portions of an image.

Tolerance

Options bar

A setting that determines how many colors the magic wand selects at a time, as measured in luminosity values.

Variations

Image > Adjustments menu

This straightforward command lets you correct an undesirable color cast by clicking thumbnail previews.