NDE Notes

Photoshop Notes - Channels & Masks

Colour Channels:
Every image opened into photoshop contains at least one or more channel. Channels are used for storing information about the colour elements in an image. The number of colour channels is dependant on the colour mode that was selected. Through

Image > Mode.

In Mode there are seven modes to choose from.

Bitmap, Greyscale, Duotone, Indexed Colour; one channel.
RGB, LAB; three channels.
CMYK; four channels.

*Channels in colour images are greyscale copies that represent each of the components of the image.

Alpha Channels
Alpha channels can be added to an image for storing and editing selections as masks.
Spot Colour Channels
Spot Colour channels can be added to an image to add spot colour plates for printing purposes.

An image can have up to 56 channels. New channels have the same dimensions and number of pixels as the original image. The file size for the channels depends on the pixel information in the channel. TIFF and photoshop formats are useful in terms of reducing channel size and information therefore giving you a smaller file size overall. You can edit a channel by selecting it and painting it.

Paint with-

White: to add to the selected channels colour at 100% intensity,
Grey: to add to the channels colour at a lower intensity,
Black: to fully remove the channels colour.

Channel Operations: Depending on the type, they can be turned on or off, copied, merged, deleted and rearranged.