Numitron clock - digit brightness

Well... there is no way to just set the brightness manually (though I think it should be added in a future release!). If you look at the Light Dependent Resistor section of the configuration screen you'll see you get basically 2 choices. If you turn Use LDR off the digits are always at full brightness. If you turn Use LDR on then the digits dim according to ambient light and you can tweak that behavior a bit by messing with Min Dim, LDR Threshold and LDR Sensitivity.

Min Dim is pretty much what it says: the dimmest the digits will ever get, even in total darkness. Larger values = brighter.

LDR Threshold: The ambient light level at which the digits will be at full brightness. Could be thought of as "offset". Larger values = reaches full brightness at a lower ambient light level than it would with smaller values.

LDR Sensitivity: Could be thought of as "gain". Larger values make the whole LDR "system" more responsive to ambient light changes than it is at smaller values.

If you find the above hard to understand, that's not you fault, I had to dig into the source code and play with one of my clocks to figure out what the threshold and sensitivity actually do! IMHO there is room for improvement here.

Cheezy Hack  
If you put a piece of black tape over the face of the LDR and turn Use LDR on, the Min Dim value will act like a manual brightness control. Larger numbers = brighter digits. Since LDR is blocked, ambient light should have no effect. Threshold and Sensitivity won't do anything either. Maybe worth a try.

EDIT: Min Dim only allows numbers in the range of 100 - 800 to be entered so you can't quite reach 100% full brightness using my hack above. My clock is quite bright at 800 and too dim to even see at 100 so I'd say you get a fairly good brightness range in spite of the limitation on value.