Enlarging images part three

A reader pointed out that after enlarging the image, sharpening done directly on the RGB image is not the best one can do.

Here is what he says:
‘I would think that performing the sharpening on the L channel (Lightness) on an image in LAB mode would provide superior results. This will sharpen without color artifacts. This is the same idea as using the K channel in CYMK, but will be much smoother – LAB has a much larger gamut. Convert back to RGB or direct to CYMK when you’re done.’

I agree with him 100%. Compare the edges of the balloons on both images carefully. On the left side I applied Unsharp mask on RGB image directly. On the right, first I converted the image to Lab Color mode (Image/Mode/Lab color) and than selected the Lightness channel in the Channels palette and applied the same Unsharp mask filter. You can spot that on the right the edges are much cleaner and sharper.

Previous posts about enlarging and improving images are here: part one and part two.

Thanks Allan for the valuable tip!