Night Vision Effect (None, Dimming, Sharpen)?

In UDL, what does this option do?

From the Help Center: Night Vision Effects This option provides alternative functionality to the Night Vision effect. Dimming causes the vision area of the selected token to become dim Night Vision 10 feet of Dimming will have the inner ten feet of Night Vision appear bright while any amount left over will appear dim from that distance onward to the end of the night vision area. Sharpen is an effect that allows the surrounding area to appear bright with a sharpening effect done on all affected areas. Sharpening can only be on by itself, and does not work with other options.