Archived posting to the Leica Users Group, 1998/10/26
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]I do indeed understand digital circuits, oscillators, mark-space ratio (actually, called duty cycle), etc... I was commenting about why, on the TTL, the LEDs don't dim. Not about what can be done, but what was done. This was a simple minded point. Sorry if I confused anyone. Jim At 09:45 AM 10/26/98 +0000, you wrote: >Jim wrote: > >> This explains why the LED's switch on/off and required a third LED >to >> show >> proper exposure. There is no such thing as a dim-able LED with >digital >> circuitry. It's either on or off. No in between. Maybe I could >learn to >> like the TTL after all. > >Actually you can. You switch it on an off too quickly for the eye to >see (say 100Hz or so) and vary the mark-space ratio. Actually that's >usually how you do it even with analogue driving circuits. > >David Morton http://www.photoaccess.com Jim Brick, ASMP, BIAA Photo Access (650) 470-1132 Visual Impressions Publishing Visual Impressions Photography (408) 296-1629