Sometimes your screen is just too bright in the evenings. For the sake of your eyes, Sunset lets you reduce the brightness of your monitor below that of the standard brightness controls and without having to adjust the backlight.
If you reduce the brightness of your screen using the on-board controls, what you're doing is reducing the brightness of the backlight bulbs or LEDs behind the screen. Sometimes that can cause buzzing, or other droning noises, and sometimes that just isn't dim enough. Sunset takes a different approach purely in software that overlays a dimming mask over your screen with different levels to suit your brightness needs.
This means that if your display makes an annoying sound when dimmed, or you just can't get it dim enough, Sunset will dim your display to your satisfaction without issue. Sure, dimming your display with Sunset doesn't affect electricity usage or the life of your backlight, but it will save your eyes at night.
The little program sits in the menu bar and can be configured to respond to global shortcut keys like F1 & F2. If you have more than one display, Sunset can dim all of them to the same level or you can pick and choose which one to dim independently. The only thing missing is some sort of auto-dimming set to a specific timer, but the manual control works well.
Sunset is great if your lowest monitor's brightness setting is just too bright, or it makes an annoying sound when not on full brightness. It's simple, easy to use and gets the job done for an introductory price of US$1.99 (regular price $3.99).