How to Use Channels in Photoshop

Why RGB Channels

Image > Mode shows your color modes – RGB, CMYK, Lab, Multichannel. Most editing happens in RGB because any color on a screen is made from red, green and blue light at different intensities; the LEDs in your display have nothing else. Those three channels are what the Channels panel displays.

Reading the Channels

Window > Channels. Clicking RGB shows the composite; clicking an individual channel shows a grayscale image where brighter means more of that color. A red jacket looks bright on the Red channel. Green hills look bright on Green. A blue sky and ocean look bright on Blue. Every part of the photo contains some of all three – the channels show relative amounts, not an on/off split.

Finding the Best Channel

Decide what you want to isolate, then look through all three channels for the one with the most contrast between your subject and everything else. For white clouds against a blue sky, Red is usually the winner: clouds stay bright while the sky goes dark. Blue is the worst choice there, because sky and clouds are both bright.

Boosting Contrast in Channels

Drag your chosen channel onto the new channel icon to duplicate it first – this matters, because running an adjustment on an original channel changes the actual colors of your image. On the copy, press Ctrl/Cmd + L for Levels and drag the black point right to crush the background to solid black while keeping your subject bright. The more separation you create, the cleaner the selection.

Making the Selection from Channels

Hold Ctrl/Cmd and click the channel thumbnail. Everything lighter than black becomes selected, with brighter areas selected more strongly than darker ones – which is exactly what gives you soft, natural edges on clouds and hair. Back in the Layers panel you can fill that selection on a new layer, or use it as a layer mask.

Finishing the Cutout

Fill the selection with white on a new layer and you have your clouds on transparency – though other bright areas of the photo will have come along too. Add a layer mask and paint out what you do not want. Put a black solid color layer underneath to check the result: every wisp of original detail is preserved, and those clouds can now be dragged into any other photograph.

Channels Quick Reference

• Window > Channels – view Red, Green and Blue separately
• Pick the channel with the most contrast for what you want to isolate
• Always duplicate the channel before adjusting it
• Ctrl/Cmd + L – Levels, to crush the background to black
• Ctrl/Cmd + click the thumbnail – load the channel as a selection
• Best for soft edges: clouds, hair, smoke, glass