Black shade and temp

[J.D. Frey]

I have an electronics question about black shading. I understand that the best practice is to black shade with temp changes, but what I'm wondering is what is actually happening. Do temp changes cause the ambient voltage on the photo sites to read as signal? Does heat cause more problems than cold? Or is there some other mechanism at work?

 

[Andre W.]

From my understanding.....

Heat generated might free electrons from the image sensor itself, thus contaminating the "true" photoelectrons. These "thermal electrons" give rise to a form of noise called thermal noise or dark current. Heat can be from the ambient temperature around the camera, or from heavy shooting. So I believe by black shading it allows this dark current to be subtracted from the image. Hence the Black Shading Calibration maps that are created.

With this in mind it makes me believe that heat would cause more problems than cold. And thats why it's always suggested to let your camera warm up before black shading, because as the sensor temperature rises, the greater you would be at risk of a few free electrons messing up the analog signal of your true signal.

Of course this is only one type of noise out of several that can occur...

 

[J.D. Frey]

Makes sense- thanks!