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How to adjust the minimum exposure time for UVC cameras

On different system, the format of the uvc camera’s attribute information report is different. Such as exposure control.

On Window system,you will see the following correspondence.

Catch

Example:

import cv2

# open video0
cap = cv2.VideoCapture(0, cv2.CAP_MSMF)

# Turn off auto exposure
cap.set(cv2.CAP_PROP_AUTO_EXPOSURE, 1)
# set exposure time
cap.set(cv2.CAP_PROP_EXPOSURE, 0)

while(True):
    # Capture frame-by-frame
    ret, frame = cap.read()
    # Display the resulting frame
    cv2.imshow('frame', frame)
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

# When everything done, release the capture
cap.release()
cv2.destroyAllWindows()

But on linux system, it throw out with another style. You can use v4l2-ctl tool to get more uvc camera’s informaton.

v4l2-ctl -l -d /dev/video0
CatchA8FD

We can see it support exposure_auto mode control and exposure_absolute control. and the control range is min=1,max = 5000, notice the unit 0.1ms.

For example, if we want to set the exposure to 1ms.

Firstly, You should open the cameara.

Then set the exposure_auto to manual mode using “v4l2-ctl -c exposure_auto=1” command.

Last set the exposure_absolute to 10 (10*0.1=1ms) using “v4l2-ctl -c exposure_absolute=10” command.

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