DBE/ABE advice needed

[neptun]

Hello. Recently i am trying to improve my processing skills with pixinsight. I never used any flat files on my old qhy9 camera and i have some vignetting in the corners of my image. Now camera is already sold to fund upgrade so it is also not an option to create such files anymore. Due to this i try to fix gradients using dynamic background extraction (DBE) or automatic background extraction (ABE) tools in pixinsight to correct the problem. Every tutorial that i have seen says to apply the DBE or ABE as early as possible which in my case means on the L, R, G and B stacks after they are aligned and cropped to match. When i do that it fixes the gradients but it also makes my useful signal much weaker and hence the whole image noisiser. I have tried different correction models (division, subtraction, with and without normalize) and result is the same. Due to that last time i decided to skip the DBE/ABE step in the beginning and applied it at much later stage - after stretch and LRGB combination. To my surprise it worked much better this way. Yes it made the whole image slightly dimmer but this time it did not reveal any noise. I used ABE at the default settings in both cases. What is your experience with this?

[jkmorse]

Hey and welcome,

DBE/ABE is not really changing your signal to noise ratio, its simply messing with how STF shows your image.  You can go in and reset STF by ctrl clicking on the little radiation symbol on STF and adjusting the sliders to get back to a better display.  If you are looking for more help, I have an 80 page workbook on most of the tools that I offer for free.  If you are interested, just drop me a note at jkmorse57@gmail.com

Best,

Jim

[neptun]

I always reset the STF and reapply it after the DBE/ABE application and when i do that the frame looks much noisier than before. I have done also another test - i make automatic stretch with STF radiation button on the integration before applying DEBE/ABE and then i transfer the STF parameters to a histogram transformation window. After that i reset the STF and apply the histogram transformation to the integration. As expected it now looks the same way as with stf enabled. Then i make undo of the histogram transformation, apply DBE/ABE and reapply the histogram transformation without changing any parameters. Now the image looks much darker than before. To me this means that after DBE/ABE my useful signal is much lower and needs more stretch than before.