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Old 31-05-2016, 08:36 AM
glend (Glen)
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Join Date: Jun 2013
Location: Lake Macquarie
Posts: 5,648
I have done some Dark & Bias comparisons for different Gain and Offset settings, there is some stretched histrogram differences but really not much at least in the 60" lengths for Darks.

For example, using the SGP stretched histogram feature, a series of 10 x 60" Darks (with camera at -25C) all come in almost identical for the same Gain and Offset setting. Using the Unity Gain and Offset preset (which is Gain = 139 and Offset = 21) the histrogram shows B 15, W 612. When the same Dark sequence is run with Gain at 71, and Offset at 12 (which are the Jon Rista recommendations), I get B 15, W 388.

Moving to Bias Frames, using the same sequence setup & temperature, ten bias frames yield:
For Unity Presets (G 139, O 21) I get B15, W 548. For Rista settings (G 71, O 12) I get B 15, W 356.

So you can see that Gain and Offset settings do have some marginal impact on the Dark and Bias frames but I don't know if this warrants efforts to capture and maintain Dark library files for different camera settings.

Opinions?
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