The alpha channel (also called alpha planes) is a color component that represents the degree of transparency (or opacity) of a color (i.e., the red, green and blue channels). It is used to determine how a pixel is rendered when blended with another.
Why are alpha channels problematic? Alpha channels allow images to use transparencies which may be rendered incorrectly by post-processing or cause processing errors.
How are they introduced? Applications such as Photoshop may introduce alpha channels automatically when 1 or more layers are not flattened prior to saving.
Alpha channels should be removed before submitting your artwork. To accomplish this use Adobe Photoshop 4.0 or higher (recommended):
- Under the Photoshop "Window" pull down; select Channels if not already visible. The alpha channel(s) and the image channel will display. Click on the Alpha Channel(s) to select it.
- To remove the alpha channel either select the arrow in the upper right hand and scroll to "Delete Channel." Or you can click, hold and drag the alpha channel(s) to the small trash can icon in the lower right hand corner. Both of these methods result in removing the alpha channel. Save the image after removal.
See screen captures below for reference.