Each pixel in a bitmap image contains three color channels, each of which represent the amount of red, green, or blue in the image. Each pixel might also have an alpha (mask) channel to achieve transparency and a depth channel that represents the distance from the camera.
By default, Maya generates an image file with three color channels and a mask channel.
To enable specific channels to rendered images, see Enable color, depth, and mask channels for rendered images.
The file size increases if an image contains a mask or depth channel. The computation time may also increase.
For information about mask and depth channels and files, see Mask and depth channels.