This filter works correctly only in the linear domain (gamma 1.0).

Incorrect working-space gamma is indicated by a superimposed gray cross-bar in the preview image.

1. Open a higher bit-depth image (or convert a 8-bit/channel image to the 15-bit mode)
2. Enter to the filter dialog and press Alt+g to open the Define screen settings -dialog.
3. Enter the system gamma space that is the gamma value from the Adobe Gamma utility (or from other system calibration utility) not the gamma value from the RGB setup.

This one-time-only 3-step setup is needed (for every DeepSpace filter) in order to have the image in the preview box to appear correctly.

USM strenght.

Radius (multiplied by 100). Radius works in 3x3 kernel by modifying the weights according to the circle of confucion. Larger kernels than 3x3 are needed only with up-sampled images (or with images that were acquired with a very soft lens). Large kernels are extremely slow when used in external Adobe Photoshop plug-ins. Therefore not implemented here.

Shadow limit per mille (from the full range). Useful with image that have high shadow noise.

Shadow percentage. Applies the specified amount of sharpening over the tonal range that is below the Shadow limit.
Use this control along with the shadow limit control to avoid areas with no sharpening at all.

Preview mode. There are 7 preview modes.

1. Shows saturation map. This can be used for gray balance evaluation.
2. Shows clipping at shadows. Shows the location of the pixels that will be clipped to level 0. The intensity of those pixels shows the clipped amount.
3. Show clipping at highlights. Shows the location of the pixels that will be clipped to maximum level. The intensity of those pixels shows the clipped amount.
4. Shows gray areas of the image.
5. Shows more gray areas of the image.
6. Shows even more gray areas of the image.
7. Shows still more gray areas of the image.

Mainly the Preview mode 3 is useful with this filter.

White-point adjustment in ev. 100 means one ev or one f/stop. -100 means -1ev or -1 f/stop.

Some image enhancement operations will peak some of the color channels of some pixels to the maximum level value. WP control is used to give headroom for the operation by expanding the range. It can also contract the range, use it when there is tail in the histogram.

Use carefully, it will clip when when contracting and scaling up too much will make the image to appear unnaturally.

Use the PV mode 3 (show clipping at highlight) when adjusting the the WP control.

Enable/Disable the Preview display.

When this option is selected the preview mode is active and the selected preview operation is applied over the filtered result.