Flats-Measuring correct exposure with statistics

[wkrispler]

Hi,

one year ago Juan Conejero explained to me how to read the process-->statistics values to judge if a flat has been correctly exposed or not.
I have a 14 bit camera so the highest value would be 16384 , a correctly exposed flat around 8000 (50% saturation).

Juan mentioned that the 14 bit dynamic range would be encoded with 16 bit in Pixinsight and therefore when I choose 16 bit in the statistics window (see screenshot) a 8000 value would be shown.

So good so fine, my flat were always ok.

Now I have the flat of a 12 bit ATIK 1600 camera in front of me. Maximum here is 4096 (2^12) and I would expect to see around 2000 in pixinsight--statistics. This is not the case, here I see for this specific flat 40491.

How is that possible? What is wrong with my interpretation?

Thank you!!

All the Best,

Wolfgang

[bulrichl]

Hi Wolfgang,

the setting of 16-bit in the Statistics process is correct.

Atik 1600? Is that a new camera with Panasonic's MN34230 CMOS Sensor (the same that is utilized in the ASI 1600MM)?

I don't have such a camera, but I read that the driver for the ASI 1600MM multiplies the ADU values bei factor 16, so a range of 0 - 65535 will result. You can easily check wether this is the case with your camera:  have a look at the histogram (in high horizontal zoom) of a flat frame and inspect the distance of neighboring intensity values. If this distance is 16, the driver of your camera behaves similarly.

40491 / 16 = 2531, I think this value would fit much better.

Bernd