PSD file
Photoshop's native, layered file format. The layers enable an illustration to be built with individual graphic elements that can be moved over and over to obtain a desired result. When the PSD format is converted into a TIFF, JPEG, GIF or other graphics format, the layering is "flattened" into one bitmapped image. For example, it would be very difficult to build a collage of many images overlapping each other without layers, because the placement of each object would have to be perfect from the start. Without layers, once a small bitmap is placed on top of the large bitmap, it becomes "one with the image" and cannot be altered at all or at least without major effort. See extension.
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| A PSD Image |
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| The image at the top is built in 23 layers plus a background layer, enabling the individual elements to be moved independently of the others. The layer window (bottom) shows each of the layers. The red arrow is pointing to the view option (the "eye") in the chip shadow layer. Clicking the eye on any layer toggles between making the layer invisible and bringing it back into view. |