View Full Version : Red colour in dark frame

fast Freddie
February 17, 2011, 21:18:48
Hi, Have a DBK21AU04.AS and have noticed that I am now getting the red colour in the top left corner when I take a dark frame. See attached. Any ideas what is causing this as it is not across the picture only in the top left corner? There are not filters attached to camera and picture has not been processed other than saving as JPEG. It looks like this straight off the camera on the laptop screen or saved to file. Thanks

February 17, 2011, 22:55:51
How long was the dark frame exposed? It looks like amplifier glow:


fast Freddie
February 17, 2011, 23:15:01
Hi, thanks for your post. The exposure was 110 seconds and from the link you attached, it looks very much like amp glow. Looks like it is getting more noticable though as the attached was taken a couple of weeks ago under exactly the same conditions but glow is a lot fainter and has a slight blue rather than red colour. Am wondering if something is failing on the camera as the glow is now much more noticable?

February 18, 2011, 01:30:42
It might be temperature related, I'm not sure. Someone from TIS can probably answer this.

In any case, if it appears in your dark frames, it probably also appears in your actual images? Is substracting the dark frames not taking care of it?

fast Freddie
February 18, 2011, 11:00:41
Hi Thanks for getting back to me. Yes it does appear in the images and is removed to some degree when I subtrack the dark frames but is not perfect. I would be interested to hear from Stephan or someone to understand why I now get a red colour and why the colour appears to be preading further across the image. Thanks

Stefan Geissler
February 18, 2011, 15:46:39

yes, it is temperature related. 110 seconds is a long exposure time, thus the camera temperature has an influence on the sensor. Therefore, some more expensive cameras have cooled sensors. The spreading on the sensor is caused by different heat radiation of the parts of the camera.