Exposure and gain settings on M7 camera

Hi guys -

Have been making great progress on my project and the OpenMV camera and IDE have helped a lot. Thanks!

I am using manual gain and exposure settings on the M7 camera. The docs say “see the camera datasheet” but frankly can’t make much sense of it. So can you please tell me:

  1. What is the range of values for gain?
  2. What is the range of values for exposure?
  3. Do you know how the exposure setting correlates to actual exposure time? I mean the time that each row is exposed, rather than the overall capture time. From what I have read elsewhere it seems as though the exposure time may depend on the frame rate and the image size as well as the exposure setting.
  4. Sort of connected to the above: I am using “sensor.set_windowing()”. Does this set the camera to capture a reduced frame size or does it crop the frame after it is sent to the processor?

If you are interested, I have the VSYNC line connected to an Arduino which I am using to switch an illuminator LED on and off. I am windowing a 30x80 pixel section out to a HQQVGA frame and am trying to use the shortest possible LED-on time. So the Arduino code is basically: wait for VSYNC, delay T1 usec, turn on LED, delay T2 usec, turn off LED. I am setting T1 and T2 by trial and error. They both seem to depend on the exposure settings (not surprising).

  • MW

Hi, being able to play with exposure settings isn’t really implemented. We just give you low level register control. That said, I can provide a document which will describe how to program the low level camera registers using sensor.__write_reg(). Email me for the document. kwagyeman@…

As for sensor.set_windowing, that’s just the processor’s DCMI cropping feature. It doesn’t affect the camera. The document I give you it’s actually for the OV7725 but a similar camera that has a similar register layout. It kinda explains nicely what to program into regs.