Iris changes the color temperature of your display. Natural light is more blue, while most artificial light (including candlelight) is warmer. Incandescent bulbs, which we’re all used to, become more red in tone when you dim them. But newer LEDs and CFLs don’t – this includes the backlight on your monitor. If you’re a photographer, you’ve probably dealt with this, since pictures taken inside at night are always much more brown than photos outside.
Iris also changes your display brightness in innovative way without PWM flickering.