Setting exposure time.

[David Haberthür]

Dear all.

I'm using tiscamera to get images from a DMM-72BUC02-ML.

I need to be able to explicitly set the exposure time for the images I get out of the camera.
This works fine with using "v4l2-ctl -c exposure_absolute=$value$", according to "v4l2-ctl -L" for $value$=1 to 300000.
I want to record the scintillation image of an x-ray pulse, which can be set in milliseconds.

I'm testing the camera in my office with an objective from you (TBL 9.6-2 C 3MP), useable exposure values are (depending on light conditions) 50 to approx. 750, looked at with "mplayer tv:// -tv noaudio:width=2048"

Does anyone of you what times the "exposure_absolute" relate to, so I don't have to empirically find out?

David

[Edgar Thier]

Hi there,

All USB cameras use v4l2 which maps camera settings to corresponding IO controls. To quote from the API specification:

Determines the exposure time of the camera sensor. The exposure time is limited by the frame interval. Drivers should interpret the values as 100 µs units, where the value 1 stands for 1/10000th of a second, 10000 for 1 second and 100000 for 10 seconds.

You can find the document here:
http://www.linuxtv.org/downloads/legacy/video4linux/API/V4L2_API/spec-single/v4l2.html#camera-controls

I hope this takes care of your problems.

Cheers,

Edgar

[David Haberthür]

Dear Edgar,

Thanks, that helps a lot! I was only looking in the man-page of v4l2, where this information is missing.

David