The idea and method Craig used was for the MINIMUM value to be around 1000 and not the maximum. This gives a bit of a buffer where at no point the black point will go to zero and thus loose data.
I always ran my settings in Nebulosity2 at a gain of 1 or 2 and an offset of 65. Black point clipping is the main concern as data that is clipped is lost forever. The black point can be adjusted during processing and some processing tasks such as contrast enhancement and shadows and highlights requires a bit of space in the black end.
Hope this helps a bit.
Quote:
Originally Posted by leinad
A quick question of gain/offset
In Nebulosity I found that
Gain 0 Offset 50 I get a Max value just on 1000. I believe thats right from what Craig Stark mentioned.
At bias 0.001 secs, this puts the histogram right to the left. Pity you cant zoom to view the histogram like MaximDL does.
http://i611.photobucket.com/albums/t...orion_test.jpg
Above was a quick stack (flat/bias calibrated and stretched) with a couple of 2min, 5min (Gain 0 Offset 55) and 1 10min (Gain 5 Offset 55).
I seemed to get similar results as well at Gain 1 Offset 110 compared against the Gain 5 Offset 55, though this wasnt good with the bias test shots.
If I understand this all correctly, I should find the right Offset with Bias frames then use that, and just boost the Gain with lights to get the best results with exp time.
Feedback welcome, thanks. |