Sharpening

Probably everyone will want to do some sharpening to the imported image. It is very easy to overdo the sharpening and induce a lot of noise which can leave the image looking very grainy. The sharpening process is probably best left until last when all the other image adjustments and so on are complete.

Photoshop has four sharpening tools under Filter> Sharpen, the only one that you will want to use is unsharp mask. Filter> Sharpen>Unsharp Mask. As a starting point for a 23mb image I'd suggest 100% @ 1 pixel with a threshold of 0. For a smaller file a lesser % might be a better start along with .75 pixel setting.

A problem with this method when a colour image is involved is that the colour information gets sharpened along with the image information, this leads to a sometimes unacceptable increse in noise, particularly in areas of similar tone, eg in skies. I find it much better to use the following procedure.

Change the mode from RGB to Lab Color Image>Mode>Lab Color. You may want to go Layer>Flatten Image before you do this.
Then in the Channels palette select the Lightness Channel by clicking on it. The image will now become monochromatic. Now apply unsharp mask Filter> Sharpen>Unsharp Mask.until you are happy with the result. Now change back to RGB Image>Mode>RGB

If you have a Lite version of Photoshop which doesn't have Lab Color try selecting the Green channel in RGB mode and apply unsharp mask to that.

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