I'm observing some temperature problem with my camera board lately. I've installed the raspberry with camera board into an outdoor-camera housing to use it as a weathercamera.
As outside temperatures reach about 0°C the image taken by the cam gets blurred (while the image center still remains relatively sharp). I haven't looked up but I guess that the camera board runs out of spec when ambient temperatures below 0°C are applied - so I'm not expecting official support on this issue. But probably someone has already experienced this problem...
As an example, have 2 pictures of today:
One can see that as soon as the sun hits the camera board directly, sharpness gets a boost. On the lower right corner you can see the outside temperature (captured by an external weatherstation) which didn't really change. I also made a script that stores the CPU-temp. each time the raspi takes a picture.
Unsurprisingly the CPU-temperature (which can be taken as a weak indicator for the temperature inside the case) shows a huge difference. @pic1: 26,1°C; pic2: 32,6°C. It stays stable, when no sun hits the camera directly.
What could be the reason for the camera to blur when it's cold? Is it possible that due to mechanical expansion of the lens/sensor/plastic the image gets defocused? Are the lenses for the camera board focused to infinite or hyperfocal when they come out of the factory (just to have a clou - if defocusing is the cause - in which direction I should pull the focus as a compensation).
However... I think installing a heating inside the housing seems to be the best long-term solution. But as a quick fix, I guess shifting the focus also could work. What do you think?
Another (more graceful) workaround could be: installing a heatpipe from the CPU to the camera board and using the dissipated heat to heat the camera. Though I'm afraid this could kill the camera board in summer...
Please, community: share your thoughts on this issue.