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Videocapture with Acer Switch 5

asked 2018-09-10 10:27:53 -0500

Andyjk gravatar image

I am having trouble setting focus on my new Acer Switch 5 tablet rear camera. This camera is focussable in Windows Camera app. Also, if I do:

pcam->set(CV_CAP_PROP_SETTINGS, 1); // To display the settings

This gets the settings window and focus is on there with a range 100 to 450. If I disable Autofocus I can move this slider but instead of focus, it seems to just be a sharpen/blur filter. Definitely not focus because at 450, distant objects are in focus and near objects are a bit blurred, but at 100 distant objects AND near objects are very blurred.

If I flick autofocus back on on the settings window, with something close to the camera, it does come into focus. However, if I then untick autofocus it immediately goes out of focus.

Repeatedly calling


only ever gives the last value of the manual slider, even when autofocus is clearly moving.

Questions: 1) Should I expect invalid values for focus (get(CV_CAP_PROP_FOCUS) if autofocus is enabled ? I was hoping it could tell me what the current focus was. 2) Could CV_CAP_PROP_FOCUS be incorrectly enumerated for my camera ? It does not seem to be 'focus' on my camera .

I am on Windows using CAP_DSHOW backend, although with auto-backend I get the same result. Opencv 3.4.1

Can anyone help?

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with computer-vision, anything AUTO* is your enemy.

berak gravatar imageberak ( 2018-09-10 10:30:32 -0500 )edit

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answered 2018-09-10 11:24:02 -0500

Andyjk gravatar image

Agreed! That is why I need to use manual focus. This camera has that functionality (unlike, for example, some front facing fixed-focus cameras). OpenCV 'sees' that it has manual focus, but it does not perform as expected. Other tablets work fine so I think it is something to do with this tablet and the drivers. I am at a loss to find a solution though

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Asked: 2018-09-10 10:27:53 -0500

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Last updated: Sep 10 '18