Photoshop Tutorials

Photoshop Color Modes & Image Colour Spaces

If you are working with photographs and other images, it is important to use the use colour modes for those images and their intended use.

The most common colour modes are RGB and CMYK.

Use RGB colour mode if you want images for on screen use, such as web sites.

Use CMYK colour mode if you want images for desktop publishing and printing.

 

To change color mode in Photoshop, choose
Image>Mode>RGB Color
or
Image>Mode>CMYK Color

 

 

General Colour Space information.

The image below shows the range of colours in the CMYK and RGB colour space.

 

Image: MikeRun [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

 

 

RGB

RGB is short for Red, Green, Blue

Additive colour model made by combining different colours of light. If you combine overlapping red, green and blue light, the result will be white light.

RGB images are used for viewing images on screen. Your computer display will display RGB colour.

 

How are RGB images created?

RGB images are composed of 3 colour channels (Red, Green, Blue).

 

There are some specific RGB standards.

sRGB is a general use colour space commonly used for consumer digital cameras, printers and computer displays.

Adobe RGB is a wide gamut RGB, which is suitable for high quality images. It displays a wider range of colours than sRGB, and is more suited to professional applications where there is a need for a wider range of colours and better colour accuracy. Adobe RGB also more closely matches the CMYK colour space used by professional printers.

 

 

CMYK

CMYK is short for Cyan Magenta Yellow Black

The CMYK is a subtractive colour model used for printing

When Cyan, Magenta and Yellow are printed one over the other, they create black (or very near black). For a true deep black a separate black ink is required as well.

 

How are CMYK images created?

CMYK images are composed of 4 colour channels (Cyan, Magenta, Yellow, Black).

 

 

How do Photoshop Color Channels work?

Each pixel, on each channel is given a value of between 0 and 255, 0 being white, 255 being black.

When these channels (three channels for RGB images, and four for CMYK images) are combined with different pixel values, they create the full range of image colours.