my take on reducing vignetting

[Daniel-K]

hi all after following loads of steps of youtube and other things heres how i reduce vignetting and gradient. now its not 100% effective it does provide a good result its mainly based on doug german's method hope this helps

Dan

step1

open your image do your basic levels and curves ( i haven't used a background layer as this is just a guide normally i would use a different layer for each action) i have highlighted the vignetting in the image as you can see it doesn't look great does it?

step2

goto image

duplicate press ok ( doesnt matter what it is called) this will then automatically open on the copied image

got Filter and select Gaussian blur and set it between 170 and 250. you will soon learn what suits the image just a bit of experimenting now press ok. as you can see in the center there's a slight glow you want to try and darken this,but if its HA nebula you want it showing or when you apply the image you will lose detail.

step3

open curves on you copied image

pull down in the middle of the curve and histogram. this will darken the image. what i try and do is to keep all the black the same, it works for me but you will learn what works best for you. press ok

select back to your original image as highlighted in the picture

step4

so now your on your main image goto image

apply image

a new box opens up i have done screen shot for the settings,

source must be the copied image name because that's the image were applying

Blending is subtract as were subtracting stuff not quite sure but it works

and the offset you can play with this i use 30-35 but you can use what ever suites your image

press ok

step5

here i have just done a curve to show you the flat background

just process the image as normally now

[JB80]

Thanks for sharing, it looks easier to follow and clearly explained over some methods I've seen.

I have a pic I can use this on so I'll give it a go.

Cheers.

[broadsword]

Hi Dan,

I suffer from terrible vignetting and gradients, and this looks like a similar method to one I found by searching for 'Synthetic Flats' on Google, involving Despeckle and Gaussian blurring in GIMP. Whilst it probably offended the purists when I created a post on it, as I have avoided Flats so far, I think it has its uses. I've had good results for bright objects like open clusters, less so for galaxies.

Neil

[Chris]

Good stuff Dan, thanks for taking the time to share:)

[ollypenrice]

OK, it will certainly help but why the resistance to flats? They will transform your images, honest injun. I say that and I'm using two imaging scopes with famously flat fields and even ilmlumination (our Tak FSQ and Yves' 14 inch ODK.) But even with these scopes flats are critical.

It seems to me that avoiding flats is harder work than making them! (SInce we've had a problem with flats in the big scope I've had to do work-arounds and I find them a pain. I hope we are sorted now. I'm about to find out... )

Olly