White Balance Settings for Nebula

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poolemarkw
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White Balance Settings for Nebula

#1

Post by poolemarkw »

I've been using SharpCap for a while now with a ZWO ASI294MC camera and always use the white balance Red and Blue sliders to line up the colors in the histogram. I'm planning to image the Rosette Nebula next and know it contains a very significant amount of red. Knowing this, how should I adjust my color histogram curves with the white balance sliders to make sure I don't over- or under-expose that red?

Thanks!

Mark
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Re: White Balance Settings for Nebula

#2

Post by admin »

Hi Mark,

my approach is always been to leave the white balance settings on the camera at their default values while capturing and fix the white balance after processing and stacking. If I'm using live stacking then I fixed the white balance using the controls in the live stacking panel. I know that other people have different views on this but that's my preferred technique.

Cheers, Robin
Billysharpcap
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Re: White Balance Settings for Nebula

#3

Post by Billysharpcap »

Hi Robin,
I know this is an old post but I am new to all of this. I have spent my time trying all the imaging software available and have settled on SharpCap Pro for my planetary and DSO imaging. Overall, for me it seems like the best and most comprehensive package so I use it from the start of a session, polar aligning onwards which is great.

When to white balance has me puzzled but this post seems to have cleared that up. I really enjoy the powerful live-stack feature but also save individual subs at the end of a session for later processing if need be.I understand that it's OK to correct white balance during a live-stack session and this data will be written into the live-stack but assume that the individual subs saved will not be white balance corrected which is OK, that can be done later if need be but I find SharpCap live-stacking so good that I haven't bothered yet.

My question is, does playing with the white balance i.e. aligning RGB curves in the live-stack histogram affect image quality? Also, does moving the brightness to make histogram corrections affect the image quality?

I am using the ZWO ASI294MC-Pro as my main imaging camera.

Anyhow, thank you for this amazing piece of software, really well thought out, it just does everything so well.

Cheers,
Bill.
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Re: White Balance Settings for Nebula

#4

Post by admin »

Hi Bill,

the answer is basically no – playing with those controls doesn't degrade the image quality of the stacked data in any way. Every time you make an adjustment to one of the colour balance or brightness settings, SharpCap goes back to the stacked image data, applies your changes to a copy of it and displays that on the screen – the actual stacked SATA is unchanged by any of these adjustments (that only gets changed when a new frame is added).

Hope this helps, Robin
Billysharpcap
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Re: White Balance Settings for Nebula

#5

Post by Billysharpcap »

Hi Robin,
Appreciate the explanation, so I am clear (your last sentence in brackets) once a new frame is added to the stacked image, any changes to white balance, brightness will be added to the overall stack not just the display copy?

I noticed that SharpCap will automatically save FIT's of each successfully stacked individual image (depending on your save setting) which is perfect for stacking later. I assume that these individual FIT's have no white balance, brightness or adjustments included in their data but PHD2 dithering is included?

I apologise in advance if above is clarified in the SharpCap manual, I have read it :-)

Being able to live-stack but still do offline stacking of the same session at another time using the offline 'Folder Monitor Camera' is a super powerful feature of SharpCap Pro that many people don't really appreciate. As an educational tool its priceless and I have been able to go back to data, re-'live' stack with my calibration frames for even better results than the 'real'-time live-stack.


Cheers,
Bill.
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Re: White Balance Settings for Nebula

#6

Post by admin »

Hi Bill,

I think we are still slightly talking at cross purposes. Let me have another go to make sure I've explained clearly:

* Any colour balance/brightness/contrast/gamma controls in the right-hand panel (except for the mini histogram stretch) affect the frame data before it even gets to SharpCap – those controls go straight to the camera software itself. If you adjust those in the adjustments end up in every live stack frame, in the final stack and in the saved raw frames.

* The adjustment sliders for brightness, colour balance and saturation in the live stacking area never affect the stacked data in any way. They also do not affect the saved raw frames.

* Whenever SharpCap needs to display the stacked image on screen or make a copy of it to save when saving with adjustments or saving exactly as seen, SharpCap copies the stacked data, then applies the adjustments to the copy, then either displays or saves that image.

Hope that makes sense, Robin
VPR
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Re: White Balance Settings for Nebula

#7

Post by VPR »

I think the confusion comes from the labels on the right Image Control tab. It would be better if they said something like ‘ch amp gain’. This would indicate that they controlled the camera directly.

I had the same miss conception till I experimented with the Image Control tab sliders and found that they indeed affect ‘raw’ file output to be used as Deep Sky imaging subs :o

V.P
Billysharpcap
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Re: White Balance Settings for Nebula

#8

Post by Billysharpcap »

admin wrote: Sat Sep 26, 2020 8:19 am Hi Bill,

I think we are still slightly talking at cross purposes. Let me have another go to make sure I've explained clearly:

* Any colour balance/brightness/contrast/gamma controls in the right-hand panel (except for the mini histogram stretch) affect the frame data before it even gets to SharpCap – those controls go straight to the camera software itself. If you adjust those in the adjustments end up in every live stack frame, in the final stack and in the saved raw frames.

* The adjustment sliders for brightness, colour balance and saturation in the live stacking area never affect the stacked data in any way. They also do not affect the saved raw frames.

* Whenever SharpCap needs to display the stacked image on screen or make a copy of it to save when saving with adjustments or saving exactly as seen, SharpCap copies the stacked data, then applies the adjustments to the copy, then either displays or saves that image.

Hope that makes sense, Robin
Hi Robin,
Perfectly clear and I appreciate you taking the time to answer this, the logic behind the interface now makes sense to me.
Cheers,
Bill.
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