Beginner's guide to image modes and colour channels

Profile

Tom Garden
 

Url

http://tg-portfolio.blogspot.co.uk

Biography

Tom is a freelance artist who, for the most part, creates concept art for the video games industry. Developing a game project of his own is his long-term goal.
 

Colour channels and image modes determine how colour is combined in your artwork. Understanding these two features will enable you to achieve better printing results and make key colour adjustments.

Under Image>Mode are the Image Modes, and changing them enables you to display the colour information differently, using channels. The colour channels displays the colour information of your piece as separate layers.
 

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1: RGB AND CMYK

RGB is the standard colour range for all computer and television displays, while CMYK is a standard format for printed artwork.

It’s useful for digital artists to work in RGB or CMYK because the artwork will usually end up being displayed using one of these formats. Note that professional and home printers now tend to employ CMYK inks rather than RGB inks.

2: CHANNEL MIXER

Click Image>Adjustments> Channel Mixer to adjust the amount of colour for each channel and their brightness or darkness.

So if you take the Red Channel, which by default is at 100 per cent, and take that to zero per cent you’re removing all the red colour information in the piece. You can adjust each channel by selecting them from the Output Channel drop-down menu..

3: SHARPENING WITH LAB COLOR


View your image in Lab Color mode and you’ll see a Lightness channel, which represents the image’s luminosity.

Apply an Unsharp Mask filter to this channel (Filters>Sharpen>UnSharp Mask): this gives you better results and enables you to increase the sharpness without distorting the image’s colour. Other filters on the Lightness channel work, too.  

CHANNEL HELP

See channels in colour


To view channels in their respective colour, go to Photoshop/File> Preferences> Interface and tick “Show Channels In Colour”.

Blending using channels

Double-clicking a new layer displays the blending options. Here you can adjust the blending using the channels, which is useful for solid colour, graphic art pieces.

Printing greyscale art

Printing greyscale artwork with a full colour range adds more subtlety to the final print.

Going from RGB to CMYK

If you paint an image in RGB that’ll be printed in CMYK, the values may change when you convert it, resulting in washed-out colours. Correct this with a level adjustment.

CMYK file sizes

CMYK files will be a larger file size because more channels are used.

More channel adjustments

Adjustment modes such as Levels and Curves also enable you to adjust channels.

Thinking ahead

Check with your client to find out how your image will be used and how it should be supplied as a final format.

Tom's tutorial was featured in ImagineFX issue 57 as part of our Core Skills workshop series.