Color balance saved to raw data?

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cwm2col
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Joined: Tue Feb 23, 2021 2:21 pm

Color balance saved to raw data?

#1

Post by cwm2col »

I have an ASI2600Mc pro and after 3 nights of imaging I cannot get my flats to work. I had to change the color balance during live view to see anything while running autofocus, but I hope that changes to these sliders did not influence the raw data. Am I expected to note down these slider values such that changes to see a live view are now forced into my raw subs?
If so, (that would ruin my only 3 night in 4 months!), is there info in a log file that I can get these values so that I can retake flats to match the R and B color slider settings.
cwm2col
Posts: 21
Joined: Tue Feb 23, 2021 2:21 pm

Re: Color balance saved to raw data?

#2

Post by cwm2col »

to be clear, I am referring to the white, Blue and Red horizontal sliders on the right hand side using this ZWO camera.
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Re: Color balance saved to raw data?

#3

Post by admin »

Hi,

the bad news is I'm afraid that the colour balance sliders for ZWO cameras *do* influence the saved RAW data. Actually, they are applied to the image data in the ZWO code before the data even gets to SharpCap. Other manfacturers have taken the other option of not allowing RAW data to be influenced by colour balance.

On the good news side, the settings should be saved in the '.CaptureSettings.txt' files that are saved alongside every capture that SharpCap does - you can just open that file in Notepad and look at all the camera settings.

Now, on the subject of flats, I wouldn't expect that the colour balance being out would have a big impact on flats working well - it is more critical that

* Use dark frames and either dark flats or bias flats when using flats
* Light frames and dark frames taken with same settings, including colour balance
* flats and dark flats/bias flats (whichever you are using) taken with same settings, including colour balance.

If you are creating a flat frame using SharpCap's 'capture flat' tool, check the box to make a monochrome flat.

Hope this helps,

Robin
cwm2col
Posts: 21
Joined: Tue Feb 23, 2021 2:21 pm

Re: Color balance saved to raw data?

#4

Post by cwm2col »

Thanks. It is very unfortunate, frankly annoying really. What is the ideal setting so I can avoid this in the future or turn it off entirely?

My flats are always monochrome with bias included and I have a separate master bias - it always works perfectly (darks not critical at all for the ASi2600 chip, and not relevant here) until i used sharpcap recently and fell foul of this setting that changed the raw lights frames. Issue is not flats but using flats with lights that have an incorrect color balance. My lights are quite different to those of a previous nights because of this setting so I had to manually match the non-neutralized histograms using Astropixel processor before calibration, which helped somewhat to get the lights RGB scales similar to previous nights and I might be able to recover them.

How can I change how an image looks in preview mode without affecting lights?
I'll check the capture setting log as all the lights for each session will have the same RGB, even when modified.

Last query - even in monochrome flats, will the RGB balance influence intensity across the frame, or remain irrelevant?
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Re: Color balance saved to raw data?

#5

Post by admin »

Hi,

personally I leave the colour balance options at the defaults (50/50 is the actual neutral default for ZWO, but it tends to leave the image rather short of blue).

You can stretch the display image (brightness stretch) without affecting the saved files (see https://docs.sharpcap.co.uk/4.0/#!2!Min ... %20Stretch), but there are no controls to tweak the colour balance of the display in simple capture mode.

In mono flats, the RGB balance shouldn't really have any significant effect on the pattern across the frame, since the colour of illumination should be constant across the frame, therefore any effect of the colour balance will be constant across the frame.

cheers,

Robin
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