Posts: 2
Joined: Thu Jun 14, 2018 7:22 pm

Long exposure with raspiraw

Thu Jun 14, 2018 7:45 pm

Hello all,

I've been trying to take long exposure (>1s) captures with the raspiraw program by @6by9, but I don't really know in which mode should I put the camera. Ideally, I'd like to capture full resolution (2592x1944) raw images (without Bayer interpolation) with the sensor's default color depth (which is 10bit for OV5647).

I'm setting the "exposure (-e)" parameter to its maximum value (2^20-1), but this doesn't seem to work and it has different behaviours depending on the "mode" parameter.

I've tried the following commands:

- ./raspiraw -md 0 -g 1 -o /dev/shm/out%05d.raw -t 20000 -sr 1 -e 1048575 -ts timestamps.txt
This seems to capture one image every 64ms. This is based on the 'delay' column of the timestamps.txt file. (also, I'm not sure if this is the time between images or the real exposure time).

- ./raspiraw -md 3 -g 1 -o /dev/shm/out%05d.raw -t 20000 -sr 1 -e 1048575 -ts timestamps.txt
In this case the 'delay' column oscillates between 1s, 2s, 3s... sometimes even more..

According to the table of modes in http://picamera.readthedocs.io/en/lates ... nsor-modes, I need to put the sensor in mode 3, where the lower frame rate is 1/6s, which is equivalent to 6s exposure time, so I was expecting to get that exposure time when setting mode 3 and the maximum "-e" parameter... but doesn't seem to be the case...

Any advise on how to get maximum exposure time with raspiraw?

BTW, I'm using a Raspberry Pi 3 with the camera module V1 (OV5647).

Posts: 2
Joined: Thu Jun 14, 2018 7:22 pm

Re: Long exposure with raspiraw

Mon Jun 18, 2018 1:59 pm


I've been playing around a little bit more and I think mode 3 is not working properly. I've taken a couple of images with the following parameters and most of them look like if they were out of sync.

Code: Select all

./raspiraw -md 3 -g 1 -o /dev/shm/test%05d.raw -t 60000 -sr 1 -ts timestamps.txt -eus 5999884 -f 0.166666667
And these are the images (they were rescaled from 2592x1944 to 1024x768):
test11.jpg (103.15 KiB) Viewed 49 times
The attachment test11.jpg is no longer available
The exposure parameter (5999884us) is the same that appears in the mmal log when I take picture with raspistill and a shutter speed of 6s.

I wasn't able to find a similar problem by reading the forum since most of the time people want to take fast captures with very high fps.
So, do you have any idea of what could be wrong?

Thanks in advance!!
test22.jpg (108.95 KiB) Viewed 49 times

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