High Pass

This transformation works by subtracting a blurred version of the input image from itself, and offsetting the result so zero is a mid-level gray. This passes through the high-frequency information (i.e. detail) in the image while suppressing the low-frequency information (smooth background variations).

Clicking on the input image display centers the 1:1 preview on the location you clicked on, or you can click and drag to scroll the preview window.

Amount

The amount control lets you control how much of the high pass 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.

Radius

The larger the radius, the more blur is applied.

Preview

A 1:1 preview of the sharpen effect is displayed in the right-hand side of the dialog box. Clicking on the input image display centers the preview on the location you clicked on, or you can click and drag to scroll the preview window.

If you enlarge the dialog box, you can make the sliders wider and the preview area narrower or vice versa by dragging the vertical separator line between them.

 Preview Button

Clicking the Preview button causes the full output image to be recalculated, not just the preview area. This can be useful if you want to view the entire image at once and not just a small section, but it can take longer to compute.