Sharpening

Most digital images require a degree of sharpening in order to look their best. Here are a few tips on how to go about it (& things to avoid too).

Shooting in raw gives you the maximum amount of control over sharpening (so do it!) However, you don’t want to apply the same levels of sharpening to every image, take their content into consideration. For example, if the image has strong edges & bold contrast, adding too much sharpening may lead to halos appearing around objects which will make them look unnatural. Also bear in mind, you’re obviously looking for a balance but in general, under-sharpening is more acceptable than over-sharpening as the latter can create images which look too doctored.

Editing software, such as Photoshop Elements, provides you with three controls for sharpening:

  1. Radius. The radius is used to set the size of the edges you want to enhance. It should be varied according to the detail in your subject. As a rough guide 0.6 is a good starting point & it should rarely go as high as 3.
  2. Amount. This is the strength of the sharpening treatment (100% is a good point to begin).
  3. Threshold. Threshold controls the minimum brightness difference that an edge has to have for the sharpening to be applied. For instance, high values will only apply sharpening to strong (high contrast) edges. If your image has lots of fine detail, a low value is required.

When you’re applying the sharpening it’s often a good idea to view the image at 100%. This way you can focus on the important details. Having said that, don’t forget to view the whole picture at some stage & check for strong edges becoming too bold or developing halos.

Don’t confuse noise with detail. Noise can be a problem in areas of uniform tone (eg. skies) so be careful not to make it more noticeable than it already may be.

How to sharpen selectively. An easy way to sharpen selectively (& thus, ensure those parts of your image which require sharpening get your attention) is to use a layer specifically for this purpose. At the end of your post processing flatten the image & then duplicate it. Now add a fairly strong sharpening treatment to it. Create a layer mask & invert it (Ctrl + I) to hide the effect of the sharpening (the mask icon should turn from white to black after being inverted). Next use a white brush to apply the sharpening where you want it. You can vary the opacity to control the visibility of the sharpening effect.

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