Masking Techniques
Using Channels

Continued.....

Clive R. Haynes FRPS

Option 2 : Replacing a sky (or to add another image)

Open the required file, copy the image

Go to the original image file, paste the new image above the original image layer.

Go to the Channels palette.

Hold down the Ctrl key and (left) click on the Channel Copy you made. ‘Marching ants' appear around the selection. Click on the Layer Mask icon at the base of the Layers palette and the selection will cut out around the mask.

NB. Should you need the inverse selection to be the ‘active area', go to: Select > Inverse (Ctrl + Shift + I) before clicking on the Layer mask icon.

Use the Brush tool and/or a Gradient to edit the mask to your satisfaction. It's often much easier to edit the Layer Mask by revealing the mask itself. Do this by holding down the Alt Key and clicking on the Layer Mask thumbnail in the Layers palette. The mask will be revealed as a high-contrast image. Work directly on this and when you're ready Alt/click on the mask thumbnail once again to review the image.

The success of the cut-out will very much depend upon the contrast and detail of the original. Some images will not succeed by this method. Should this simple copy & paste method be not as effective as you would wish, an alternative is; ‘Masking & Cutting-Out with Channel Mixer & Alpha Channels' – see link below. This method offers refinements for more accurate masking.