Trouble with the correct vignetting tool (still!)

@pete_xl

Hi Pete,

I see what the vignetting tool does, only I don't understand why you use it?

In the before shot I can't see any clear signs off vignetting?

As far as I know this tool only will be useful when you've got strong vignetting, that can't be removed with flats.

Do you use flats?

As I see you're befor shot I would never use the vignetting tool (never used it for myself).

Clear skies Jan-Willem

@jw_duijndamhetnet-nl

Hi Jan-Willem,

thanks for your response! But aren't all types of vignettes eliminated by the use of proper flats? I thought this tool in APP was made to heal vignetting for to avoid having to take flats.

I choosed this example image because I wanted to show that in my case the tool even applies a white vignette if there is nearly mothing to do for it. The image was taken with my 130/910 mm at native focal length. If I use my reducer or the other telescope which is an 80/480 mm refractor there is significantly more vignetting to care for. And also in these images which have a stronger dark vignetting APP always applies a weird white vignette.

It is my understanding that if there is a software tool for eliminating vignettes in APP I would like to use it exactly for that. I do seldom shoot flats. Most of the times I handle the vignettes quite easy with the APP light pollution tool or later in PS. But I really would like to eliminate them with the tool that was made for this and/or also would also love to create artificial flats in APP.

Clear skies and less rain

Pete

I've seen this problem for at least two of the latest versions. I may be mistaken, but I thought it worked pre-1.074. I think the vignette removal tool is on low priority now as other very useful features have been added.

I am an early (and happy) customer of APP and I had this effect from the beginning. I can live with it and I would be ok if I knew that all the other users have the same effect and that I do not have to feel alone with the problem.

Posted by: @pete_xl

I am an early (and happy) customer of APP and I had this effect from the beginning. I can live with it and I would be ok if I knew that all the other users have the same effect and that I do not have to feel alone with the problem.

You are not alone 😉 but I could swear it worked at one point. But I know that in the last year and a half that I had a bad light pollution problem that looked like vignetting. It turned out I had swapped out the extension tubes with new ones that were in fact not good - at a star party. The new ones had shinny inside surfaces that created a fog in the middle of the image. I thought it was vignette but then I remembered that I didn't get much vignetting originally with my rig. Its so long between uses of my scope and I'm pretty new so I didn't realize at the time what was happening. A local dealer noticed the problem when I went to them for help. Anyway, I definitely had and still have the problem you mention when I try the tool but I don't really need it now 🙂

Hope you all had a nice Christmas! Sorry, been away during this period.

So, the vignetting tool is definitely not a replacement for taking flats. Flats (when done right) will always give you the most accurate calibration possible + will get rid of any dust you might have in the image. It's a tricky tool I agree, I think it'll be explained well in the upcoming manual. I think the overcorrecting might have to do with the noise level in the image, if you calibrated that well with bias at least, it should work. But you also need to have a gradient that does make sense to fix, for instance there isn't any clear one in the image above. I'll see if I can come up with an example.