Click for a video about Layer in GIMP (a popular open-source image editor) – 5 minutes.
Click for a video about Layers in Photoshop Elements – the super simple explanation ! – 10 minutes
So what IS a LAYER????
Layers are one of the most powerful tools included in many photo editing programs. Adobe Photoshop Elements and Adobe CS3 are two examples of programs that make use of layers to allow photographers great control in editing their images. Layers are exactly what they sound like. They are images or effects overlaid on top of one another like several sheets of plastic and then stacking them together. These sheets of plastic can be either clear, opaque, or anywhere in-between. These layers can also hold part of an image or a whole image. By stacking these layers together we can create exacting adjustments to our images, combine multiple images, or create new images. Using layers has several advantages over making adjustments directly to an original image.
By using layers you can make adjustments without changing the data of the layer underneath. This allows you to make multiple changes without having to start over each time an edit doesn’t turn out like you had intended.
Avoid Data Loss
Each time you change your image through adjustments or other edits, a small amount of data can be lost. By using layers, your original image is protected from corruption Just remember to use “save as” and not “save”. That way you will not have lost your original photo data.
Specific Point Editing
By using layers you can select just one part of an image using masks (or by deleting the unwanted part on just one layer). This allows you to edit foregrounds, subjects, and backgrounds separately.
Quick Edits to Multiple Images
By copying your editing layers to other images you can quickly make adjustments to large numbers of images. The first step in working with layers is creating a new layer. Most photo editing programs use a layer menu option. There are several options for types of layers to accomplish specific tasks. The basic layer type is simply a blank layer placed on top of the current layer. This type of layer can be either transparent or opaque. If you have several layers open already you can chose “layer from background” to create a new layer from the original background layer. You can also use “layer via copy” to make a new layer from items selected on the current layer. Fill layers area quick way to create a layer filled with a solid color, gradient, or pattern. This type of layer will most often be used in creating images from scratch rather than photography editing.
Adjustment layers are layers used to adjust characteristics of the background (original) image. Items such as levels, brightness/contrast, hue/saturation can be adjusted using adjustment layers. Options for more advanced changes such as invert to create a negative effect are also available under adjustment layers. Once you have created a new layer (or layers), you will be able to view your layers under the layers display (usually on the bottom right hand side of your screen). The layers are shown in stack order. That means that the level on the top of your display list is the top layer of the stack.
The small eye icon beside each level indicates which levels are currently visible. The level highlighted with light grey represents the level that is currently selected (any actions will affect the selected level). The opacity indicator at the top of the list allows you to change how opaque or transparent the selected layer will be. The selection that defaults to “normal” is the blending mode option. This tells the program how to blend the layers into one overall image.
The best way to learn these options is to experiment with them. Layers can be reorganized simply by clicking and dragging them to a new position. Remember that adjustment layers only affect layers beneath them in the list.
Article courtesy of Liz Masoner, photographer