Ambient light sensing via LED response

pgf at pgf at
Sat May 2 08:38:59 EDT 2009

john wrote:
 > By the way, has anyone really thought about this feature ?  I grok  
 > the intent, but you have to make
 > sure that kids who happen to be in brightly lit rooms (glaring  
 > fluourescents aren't uncommon)
 > don't loose their backlight, and wonder why ?   The keyboard lighting  
 > on my mac is a good idea,
 > but they only allow adjusting the amount of light output, not the  
 > sensitivity to ambient light.

i've been wondering about usage, as well.

we had a dedicated light sensor on the last product i worked on
(which, in retrospect, given that it had 15 watts (!) of
backlight seems like maybe the wrong place to have started trying
to save power ;-).  i implemented a proof-of-concept algorithm
for automatic control, but found it a little weird -- it always
felt like there was something wrong with the backlight as it
shifted up and down in brightness, even with a fair amount of
averaging and/or delay.  plus we never resolved how it should
interact with the actual brightness buttons.  after all, if you
adjust manually, you're probably unhappy with the setting that
was chosen automatically.  so should manual control abort any
automatic algorithm?  or maybe the buttons should tune the
algorithm?  how?

i'm suspect there are answers to all of these, but one of the
feature's champions should be thinking about it...

(in the end we never finished or released the photosensor
support, because it turned out the usage pattern of the device
(an automotive diagnostic tool) meant it was almost always
fully powered, either from the wall or the vehicle it was

 paul fox, pgf at

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