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Night mode: video is dark - image is bright?

Posted: Sat Feb 14, 2015 10:31 am
by egmontr
Hi together!

I have a problem with the RPi cam and the night mode.
When I am recording an image in night mode it is bright and clear. But if I am recording a video the video is very dark. The setting are the same.
I tried it with raspistill and raspivid and with RPi Cam Control 4.2.3.

Am I doing something wrong, or it not possible to record a video in night mode to be as bright and clear as the recorded image?

Egmont

Re: Night mode: video is dark - image is bright?

Posted: Sat Feb 14, 2015 10:42 am
by jamesh
Night mode is problematic when using video. 30fps video requires a max exposure of 33ms per frame, night mode works by trying big exposure times, much bigger than that. These don't work well together!

So since video forces a max exposure, the video is dark.

You could try lower frame rates, not sure how that might work.

Re: Night mode: video is dark - image is bright?

Posted: Sat Feb 14, 2015 10:48 am
by 6by9
jamesh wrote:You could try lower frame rates, not sure how that might work.
It should work fine. 15fps would allow 66ms exposures. Night mode in theory allows up to 0.7sec exposures, which would require 1.4 fps or less.

Re: Night mode: video is dark - image is bright?

Posted: Sat Feb 14, 2015 2:00 pm
by egmontr
Thank you james and 6by9. It works fine.

The only thing is, that then the motion is faster on the projector (for example VLC). I found the option for slowing down the motion in VLC and then it is quite good. Not so clear, but OK.
I used 10 fps and exposure night. With 5 fps the video is very unclear but very bright.

Re: Night mode: video is dark - image is bright?

Posted: Sat Feb 14, 2015 2:19 pm
by towolf
You can also set --framerate 0. Then FPS will be completely variable with a max of 30. This is problematic when you write an .h264 file, since it will make a variable speed video. But for network streaming or muxing into container that supports variable frame rates it works fine.