A lot of Android devices have screens that are too bright for nighttime reading even on the lowest official brightness setting. For many rooted devices, this can be fixed with my free
RootDim (formerly known as SuperDim).
Last week I figured out how to do this without root, and yesterday I released ScreenDim, a paid app ($0.99) that allows dimming the screen below the lowest official brightness setting on many devices. Root is not needed. ScreenDim also lets you adjust the contrast for even dimmer viewing, and (this is experimental) and turn off button lights. You can also set five presets, and create launcher shortcuts to them.
It is now
in the Market (with a free trial available). For devices that don't have the Market, it is awaiting approval in Amazon's app store--in the meanwhile, non-Market users can download a 10-day trial
here. Hopefully by the time that expires, it'll be in the app store.
You may wonder how this differs from the very clever free
ScreenFilter app (which in fact inspired ScreenDim, though I think it works a bit differently). There seem to be two main differences. First of all, on LCD devices, as far as I can tell, ScreenFilter does not dim the backlight below what the OS allows. It simply decreases the contrast, I think by drawing a dark overlay. The visual effect is the same as the contrast slider in ScreenDim. But this method keeps the backlight glowing through the blacks, and in the dark that makes the blacks grayer. The better way is to use the brightness slider in ScreenDim and keep the contrast at 100%. (On OLED devices, this may not make any difference since there is no backlight.) Secondly, I spent a good deal of time benchmarking on my Archos 43 with AnTuTu, and ScreenFilter seems to slow down the 2D graphics speed by about 30%, while ScreenDim does not produce a noticeable slowdown, whether you use the brightness or the contrast slider (I think there may be a
very small slowdown if you put the contrast slider below 100%).