Sharpen

This transformation creates a sharpened version of the current image. Images are sharpened by exaggerating the difference between each pixel's value and the average of its neighbors. This technique makes edges more distinct and gives the appearance of greater sharpness. The Sharpen transformation is useful for slightly sharpening an image – to get a stronger effect, use either the Bilateral Sharpen or Advanced Sharpen transformation.

Amount

The amount control lets you control how much of the sharpen transformation is applied to the input image. You can apply a percentage of the transformation to the entire image, or you can specify an amount mask to restrict the effects of the transformation to only part of the input image.

Method

This control lets you select the sharpening method.

Sharpen -- exaggerates the difference between each pixel and the average of its four nearest neighbors.

Sharpen More -- exaggerates the difference between each pixel and the average of its eight nearest neighbors

Halo Limit

This control has two sliders for limiting light and dark halos. Halos are sharpening artifacts and appear as light or dark areas around boundaries in the image. If you notice such a halo, reduce it by moving the appropriate slider to the left until the halo is no longer noticeable. Limit settings in the range of 5 - 15% are typical.

Threshold

This slider can be used to reduce the tendency to increase noise in the input image. When sharpening an image, the input image is first compared to a blurred version of the input image. If the absolute value of the difference is less than the threshold, no sharpening is done. Thus, a threshold of zero causes the entire image to be sharpened (except for regions partially or totally excluded by a mask). Large threshold values cause the sharpening to be applied only to very strong and sharp edges. A value of 0 yields full sharpening; higher values eliminate sharpening of increasingly coarse detail. Typical values are in the range 2 – 5.

Sharpen Factor

The greater the sharpen factor, the more pronounced the sharpening effect. At 0% you get no sharpening; at 100% you get normal sharpening; 200% you get double sharpening.