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Photoshop Techniques – Selective Sharpening for the Scene

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Here is the sharpening technique demonstrated in the Digital Group meeting 11th July

Guy Gowan is the source for this channel based sharpening technique, have a look at www.guygowan.com

A subscription to his website will get you the tutorials as well as his action set.

Selective sharpening can be well done on individual images by sharpening and masking, but this is a manual process.

This workflow can be automated by means of an Action and applied to all images.

If you subscribe to Guy’s website you can download an automated action set.

Start by right-clicking, downloading and opening this 2.8MB 16MP jpeg (in real life, better to start with a RAW file) of our portrait model Beth.

Do not apply any RAW sharpening.

Have your Layers and Channels Palletes open (they should always be visible)

Ctrl-Alt-J to copy the background layer, name it Sharp, select that layer so that you are working in it.

Zoom to 100% so that you can see Beth’s face clearly. The image is well focussed but soft.

Now Ctrl+Click on the Red channel (of the Sharp layer)

This creates a selection of the greyscale of the Red channel. Note how nicely the cheek is framed.

Select-Inverse to invert the selection, Ctrl+H or View>Extras to turn off the marching ants

>Filter>Sharpen>Unsharp Mask and set to 500, 2, 0

Note how the highlights have been sharpened and there are no horrible white lines, the skin is not over-sharpened but we can fix that later if we wish. Note that the edged contrast between the smooth cheek and dark hair has no ugly halos.

Although not bad in this image, the shadows have received some sharpening (not as bad as a normal Unsharp Mask as we have allowed only a small amount of sharpening in the shadows due to our mask selection

Let’s use the layer properties to bring forward the darker parts of the background (soft, unsharpened) layer to soften the sharpening artifacts in the image.

Double-click on the Sharp layer to bring up the properties box.

Alt-Click on the dark slider of the Underlying layer to bring the details forward. Dividing the slider gives a soft gradient, 100% of Level 0 is brought forward reducing to 0% of level 128. The position of the RHS slider is image dependent. This action has some slight effect on the midtones and no effect above that.

Automate this process if you like and adjust the slider afterwards.

The Channel selection should be done by checking the channel mask.

Red is good for portraits because it has smooth tonal graduations in the large areas of skin and sharp contrast in the eye highlights.

A selection of the Blue channel however, would cause seriously ugly skin sharpening.

Change the opacity of the Sharp layer to control the amount of sharpening, but 100% already looks really good on print.

If you wish to smooth the skin, create a mask on the Sharp layer and use a soft black brush to paint over the parts of the skin where you want to remove sharpening.

Posted by Barney 15/07/2011