A Simplified method for using Lab Sharpening
One of the methods we have taught in the past was Lab Sharpening. Lab sharpening has the
advantage that as we are only applying sharpening to the luminosity channel only the
lightness/darkness of the pixels are effected meaning we don’t get any unwanted colour
artefacts produced. The original method was a bit convoluted and required we change the
mode from RGB to LAB mode then apply sharpening only to the L (Lightness) channel before
switching back to RGB.
Due to the complicated way we had to do this sharpening it never became popular.
There is however a simplified way of doing almost exactly the same thing.
After we do all our ‘Photoshopping’ to an image we are ready to apply sharpening.
I like to do this on a separate layer and I often make a ‘stamp’ layer for this purpose. Make sure
the top layer is selected then, while holding down Alt go to the little down arrow on the right of
the layers palette and select Merge Visible from the dropdown.
South Shield Digital Group
C McNair
April 2015
A new layer is produced which combines all the lower visible layers into one.
Filter>sharpen>unsharp mask. Now these settings depend on the image, but a good general
starting point is the values 120/1/3 for Amount/Radius and Threshold. Click Ok.
South Shield Digital Group
C McNair
April 2015
After we apply the filter and before we do anything else choose Edit>fade Unsharp mask. A
little dialogue box appears with a slider which allows us to alter the opacity, but the key thing
with this dialogue box is to change the blending mode to Luminosity.
Click Ok.
If the sharpening is too strong reduce the opacity of the layer.
If the sharpening isn’t strong enough reapply the Unsharp mask filter and if it is now too strong
reduce the opacity of the top layer.
Done!
South Shield Digital Group
C McNair
April 2015