We all want our photographs to be sharp as can be, and that begins when you take the shot in the first place. A camera on a tripod, sharp lens, accurate focus, all go to assist you. Afterwards though, you process in photoshop or lightroom, and you can get something extra.
Sharpening is best done at the very end of any other processing that you do – as other things can actually soften the image slightly. So what’s the best way….
I use unsharp mask in CS5 – it uses the same engine as Lightroom 3 – and you should get the same results. Oversharpen an image, and it can result in a halo where dark parts of the shot, meet lighter ones. This is caused because when sharpening happens in the software pixels are either lightened or darkened to make edges seem clearer. Oversharpening can emphasise this difference, and you see the halo.
So, you look at the unsharp mask settings, and there are three sliders, Amount, Threshold, and Radius.
Amount is about how much you want to sharpen the image. The higher the number, the sharper it looks, but overdo this, and you will get the ‘halo’ effect.
Radius – this affects how many pixels away from the edge the sharpening will be applied to. Low numbers mean the effect is more exaggerated. The higher numbers will start to soften the effect slightly.
Threshold defines what the software thinks is an ‘edge’ – the higher the number, the more difference there has to be between pixels before it is counted as an ‘edge’.
So what’s a good setting to use ? Well that all depends on the image – some (like landscapes) can stand more sharpening than others. Portraits can stand being sharpened around the eyes and hair, but you would want the skin to be less defined.
Remember that when the image is finally printed, it can lose some definition, so oversharpen slightly for this reason.
In the shot at the top of the post I used the following settings…. amount 65%, radius 1, and threshold 3.