Green predominance

Somewhere to ask questions about the best way to use SharpCap
Post Reply
a-po
Posts: 3
Joined: Thu Apr 16, 2020 5:34 am

Green predominance

Post by a-po » Thu Apr 16, 2020 5:50 am

Hi,

I’ve been using Sharpcap for 18 months and I keep learn. This is my first message here. So, Sorry for my english it’s not my first language.

Since I aquired my new cam a few weeks ago, an ASI 533, I’ve noticed a predominance of green. Maybe did I have it before with my former one, a 224 ?... I don’t know I sold it.

I join an image of a uniform capture from a geoptik flat box to illustrate.
41297A63-F5C4-4F9A-BC68-B73B3E6E856F.jpeg
41297A63-F5C4-4F9A-BC68-B73B3E6E856F.jpeg (366.14 KiB) Viewed 435 times
Is it normal ?
Is there a cam issue ?
A parameter I missed ?

Thanks for your advices.
And don’t hesitate to reorient me if there is already a topic on it.

Anthony

User avatar
admin
Site Admin
Posts: 4476
Joined: Sat Feb 11, 2017 3:52 pm
Location: Vale of the White Horse, UK
Contact:

Re: Green predominance

Post by admin » Thu Apr 16, 2020 9:52 pm

Hi,

You have two ways to try to deal with this problem – one is to turn up the controls on the right-hand side marked 'White Bal (R)' and 'White Bal (B)' – this will boost the red and blue channels to give you a better white balance. However the downside of this is that for most cameras the boost is performed digitally in the camera software after the images come from the camera and before it gets to SharpCap. This can cause loss of data (signals for the red and blue channels that were not saturated may become saturated due to the boost).

Another possibility is to ignore the green image while you are capturing and deal with it when post processing your final image – after stacking, dark subtraction, flat correction etc.

Hope this helps, Robin

a-po
Posts: 3
Joined: Thu Apr 16, 2020 5:34 am

Re: Green predominance

Post by a-po » Thu Apr 16, 2020 10:13 pm

Ok I understand. Thanks !

mAnKiNd
Posts: 303
Joined: Sun Jun 11, 2017 4:55 pm
Location: Long Island, NY
Contact:

Re: Green predominance

Post by mAnKiNd » Thu Apr 16, 2020 10:25 pm

To add to Robin's response, I tested some light pollution filters that selectively interfere with certain "offensive" wavelengths, in order to see if there was a filter that could mitigate the green cast and render a more neutral white balance during acquisition. Although my findings are not comprehensive nor conclusive and their generalizability should be interpreted with caution (i.e. different camera sensitivities etc..), it might provide you with some info about which filters help tone down the Green Hulk monster that lives inside our OSC camera bayer matrices :mrgreen:

viewtopic.php?f=9&t=2298

Hope this helps.
Minos

nexusjeep
Posts: 206
Joined: Thu Oct 18, 2018 3:01 pm
Location: Gloucestershire

Re: Green predominance

Post by nexusjeep » Thu Apr 16, 2020 10:36 pm

My ASI2600 will do similar all I do in live stack is use the auto colour balance button in the histogram tab and then manually tweak the red / blue sliders again in the live stack histogram to get a black background so that the live stack looks okay. I restack outside of SharpCap for my final image so adjust colour there afterwards in APP / CS2020.

in the normal view I always get a green cast simply because of the RGGB arrangement, but this is only when I am plate solving / polar aligning / focusing as I spend most of the evening in live stack mode.

My flats always have a green colouration.

Cheers
Nick

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

Re: Green predominance

Post by Rab722 » Fri Apr 17, 2020 2:19 am

I also have a 533 and recently had similar questions about using the camera with Sharpcap. Check these 2 threads.

viewtopic.php?f=29&t=2503

viewtopic.php?f=19&t=2491

Its normal for green to dominate as there are 2 times as many pixels with with green filters in the Bayer pattern. I now just leave red and blue gain in the image controls at 50% which is a gain of 1. Then when stacking just select the icon below the sliders to balance the colors. Much easier than fussing with the red and blue controls and trying to balance the colors.

Post Reply