3 ms·

Why would an autofocus routine use a timestamp? Boggle me confused.

• plaes 17y ago
  Well, there are many options how to do autofocusing, but one of them involves sending out either ultrasonic or infrared wave and calculating the delay it takes to cover the distance to the subject. Now lets just hope that someone with more knowledge about the implementation of this system can describe the problem more clearly...
  • agravier 17y ago
    I'd like to point out that if we assume that the infrared wave travels at the speed of light in empty space (I know it's somehow slower but good enough for the back of this virtual envelope) to a subject 1.5m from the camera and comes back, the total time would be 10.007 nanoseconds, so the timer should be accurate enough to measure fractions of nanoseconds to perform a correct autofocus. So, I don't think that's how it works. Now, for the sound wave, maybe?
• natrius 17y ago
  My guess is that autofocusing is based on input collected over a period of time, not instantaneous input.
  • jacquesm 17y ago
    Some implementations are (this one appears to be), but not all of them. For instance, one simplistic way of focusing automatically maximizes the contrast in the area of interest.
• deleted 17y ago
  [deleted]