How to set As Lower Brightness as in Clock application, without rooting I noticed that with the Froyo "desk clock" application, when you put it in low light mode, it forces the back-light far darker than you can manually make it in the settings. 

My question is: is there an application or a non-root hack that can make the back-light really dim just like in the desk clock application?
As that clock can set brightness lower without rooting, there should be a way to do that without rooting.
The Clock app is setting flags on its own fullscreen window that override the system default screen brightness, but this only affects that app's window.

See the source for DeskClock.java

 551             winParams.flags |= WindowManager.LayoutParams.FLAG_FULLSCREEN;
 552             winParams.dimAmount = DIM_BEHIND_AMOUNT_DIMMED;
 553             winParams.buttonBrightness = WindowManager.LayoutParams.BRIGHTNESS_OVERRIDE_OFF;


The flags used are documented on the Android Developer site, in particular:


  float BRIGHTNESS_OVERRIDE_OFF Value
  for screenBrightness and
  buttonBrightness indicating that the
  screen or button backlight brightness
  should be set to the lowest value when
  this window is in front.


So, the DeskClock is not using anything special to dim the screen, but it can only affect its own window.