Image Controls for Darks and Flats

Somewhere to ask questions about the best way to use SharpCap
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Rab722
Posts: 16
Joined: Mon Mar 02, 2020 12:20 pm

Image Controls for Darks and Flats

Post by Rab722 » Tue Apr 07, 2020 7:37 pm

I'm using a ZWO ASI533mc and I have the following settings in the Image Controls Panel.
Brightness , White Balance (Red) and White Balance (Blue)

Is there any adjustment to these needed before creating darks and flats.

Also what are the best practices to using these controls before capturing. My live stacks always end up with a red green or blue hue to them.

BlackWikkett
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Joined: Sat Jun 23, 2018 8:48 pm
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Re: Image Controls for Darks and Flats

Post by BlackWikkett » Tue Apr 07, 2020 9:30 pm

Brightness is ZWO's term for black level or offset. This gives a boost to all pixels captured. When looking at the histogram adding brightness moves the histogram off the left edge in effect making sure you don't clip data / black level.

WB red and blue allows adjusting the data for red band blue pixels directly at the camera. If you use this, which isn't necessary if live stacking, you'd adjust levels to attempt to balance the red and blue signal with green level to get a white balance. Recommend leaving the red and blue white balance at 50 and adjusting white balance with the color sliders in live stacking.

Regardless of how you proceed make sure that red and blue white balance and brightness is the same for darks and lights or you'll get color gradients. For flats I always leave the red and blue white balance at 50 and brightness at 0.

-Chris

Rab722
Posts: 16
Joined: Mon Mar 02, 2020 12:20 pm

Re: Image Controls for Darks and Flats

Post by Rab722 » Wed Apr 08, 2020 1:16 am

Thanks that helps. I will redo my darks and flats with those settings.

With the cap covering the camera for darks I tried adjusting the brightness and viewing the histogram. Here are the counts in RAW16 for different brightness levels for the ZWO ASI533

Brightness, Counts
0, 0
10, 384
20, 772
30, 1184
50, 1984
100, 3970

So each percent increase is about 40 counts.
I then set the brightness (offset) at 50% and moved the red and blue balance sliders off the 50% mark and it appears they are applying a gain

White Balance (Red and Blue) , Gain
0, 0
25, 0.5
50, 1.0
75, 1.5
100, 2.0

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