Astrofreak85
Posts: 4
Joined: Mon Feb 03, 2014 11:41 am

Problems with AWB and night shot

Mon Feb 03, 2014 12:34 pm

Hello,

I tried to use the Cam for Day/Night timlapses.

I've encoutered two problems:

1. I use ex=night as setting, the exposuretime is quite fine until twilight until it hits the maximum of 1/1 secound, from one frame to another it starts to take the frames only with 1/4secound until mornig twilight where ist starts to take from one frame to another again pics with 1/1 secounds...I'd like to have 1/1 secound for the whole night...whats wrong here?

2. Althoug I've set awb=horizon the awb seems to differ from image to image some frames are redish, some are more blue etc. why doesn't stay the colour of the pics constant when awb is set to a value?
When I set awb=none I allways get totaly black frames....?!

The raspistill command is triggerd once every minute via a cronjob.

I hope somebody could help me here...

Thanks,
Astro

poing
Posts: 1131
Joined: Thu Mar 08, 2012 3:32 pm

Re: Problems with AWB and night shot

Mon Feb 03, 2014 1:10 pm

My guess is you have to use a long -t value like -t 10000 (ten seconds). In this period the camera decides on exposure by taking frames and analyzing them. If you have a shutter speed of 1 second -t 10000 will have 10 frames to decide, if you use -t 1000 only one frame, which is too short. If you take a video at night you can see the brightness changing and can measure about how long the camera needs in your situation.

Street lighting is often oscillating with different colors. Although 1/4 sec is pretty long it could be that increasing the shutter speed (and -t value) will help.

Astrofreak85
Posts: 4
Joined: Mon Feb 03, 2014 11:41 am

Re: Problems with AWB and night shot

Mon Feb 03, 2014 2:11 pm

ok, I'll try this.
At the moment I use the standard value (I think this is 5sec?)...

Astrofreak85
Posts: 4
Joined: Mon Feb 03, 2014 11:41 am

Re: Problems with AWB and night shot

Mon Feb 03, 2014 2:29 pm

ok, now the command looks like this:

Code: Select all

raspistill -t 10000 -n -ex night -awb horizon -mm matrix -q 85 -w 1280 -h 920 -o /media/16GB_MARKUS/$filename
Just waiting for the night...hope its better now....

strange thing is, that the changed AWB and Exposure settings don't show up in the exif data of the picture....did I something wrong in the command above?

Code: Select all

ExposureProgram - Aperture priority
ComponentsConfiguration - YCbCr
ShutterSpeedValue - 1/375 seconds
ApertureValue - F 2.90
BrightnessValue - 2.84
MaxApertureValue - F 2.90
MeteringMode - Average
ExposureMode - Auto
White Balance - Auto

jamesh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 23382
Joined: Sat Jul 30, 2011 7:41 pm

Re: Problems with AWB and night shot

Mon Feb 03, 2014 3:56 pm

We think there may be an issue with some of the EXIF data in some cases. Not had time to check out what it might be.
Principal Software Engineer at Raspberry Pi (Trading) Ltd.
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Astrofreak85
Posts: 4
Joined: Mon Feb 03, 2014 11:41 am

Re: Problems with AWB and night shot

Mon Feb 03, 2014 5:06 pm

great, at least the problem with the exposure time seems to be gone :)

now the only problem left, is that AWB changes, somtimes from pic to pic...
ther doesn't seem to be a diverece between the AWB-Modes...except that "none" gives me a black picture...

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