Since posting about sharpening the past few weeks, a number of people have asked what the numbers for USM mean (Unsharp Mask). So this week I will explain the components to USM sharpening in simple terms.
The “amount”controls how intense the sharpening is. The lower the number, the weaker the sharpening, the higher the number, the stronger the sharpening. Higher is not always better though so be careful. This has to do with the amount of contrast between pixels.
One thing to keep in mind is print size and also how big a file you are working on. The larger the file, the higher you can do this. If you are working on a smaller file, you will keep this a lot lower.
The radius deals with the width of an area – how wide an area around the edges is sharpened. A low number affects very close to the edge or just the edges. A higher the number, the more you will be sharpening away from the edge too.
The threshold deals with tonal differences. There has to be tonal difference before any sharpening takes place. The higher the number, the more tonal differences are taken into consideration and sharpened. The threshold helps areas of similar tone not get sharp (like skin that you want nice and smooth). This number usually stays low, especially for portraits. If you want a photo to have a noisy look (purposely), you can increase this number as it will sharpen more like tones.
STAY TUNED NEXT WEEK for some numbers. I will give you some numbers to play with for USM sharpening. So keep watching for these.