First test of Background Substraction (from Folder Monitaor Camera)
Hello Robin,
I just installed the Beta version and begun to play with Background substraction with the folder monitor.
I use SharpCap in Livestacking mode mainly; I keep the unitary lights for further processing but I love the ability to enjoy the on-going acquisition
Here are my first feedbacks on the feature:
- in my case, the colour are better balanced after activating the effect, there is a shift upwards of the histogram (!), I don't understand why:
- Background level with no dark or flat : ~3500ADU (in RAW 16; taken from an ASI533 camera) [first attachment, only autostretch on mini histo, main histo is reset]
- BG_nodark.jpg (247.41 KiB) Viewed 2483 times
- Background level with dark + no background reduction : ~300ADU [2nd attachment]
- BG_withdark.jpg (251.27 KiB) Viewed 2483 times
- Background level with dark + now background reduction is activated : ~16500ADU [3rd attachment]
- BG_withdark and with background reduction.jpg (209.77 KiB) Viewed 2483 times
Having a sky background at 25% of the histogram is not really an issue, you have black and mid level to play with. My main issue was for the "final colour balancing", in the following capture, I made a strech with the mian histo in order to see the small discrepancies in background colour balance.
It is a full stack (54 images instead of 1 in the previous captures)
Usually, I make the colour fine tuning with the pad arrows, 0,02dB increment.
- one attachment with no colour adjustment : a little too much green in the sky backgroun
- BG_withdark and with background reduction_fine colour balance 1.jpg (147.16 KiB) Viewed 2483 times
- one other attachment with -0,02dB on the green level : now the green is much too low !
- BG_withdark and with background reduction_fine colour balance 2.jpg (155.46 KiB) Viewed 2483 times
My understanding is that the colour adjustment in the main histogram impacts the image before the "Background substraction" is applied and as a consequence the smallest colour adjustment have now a big impact which makes these adjustments not usuable
I don't know if these feedbacks are relevant as I was in folder monitor mode but I think so. In all the case, I think this feature will be very usefull, not only for the light polution but also when you use filters which may impact the colour balance between channel, in some cases the colour adjustment with the main histo may be tricky.
Best
Jean-Baptiste (from France)