DSS and hot pixels

[BrendanC]

Hi all,

I recently noticed that some of my images still have hot pixels even after running them through DSS with hot pixel detection turned on. I'm (fairly) sure my darks library is ok. If I use the 'Cosmetic' tab to auto detect and clean hot and cold pixels, it fixes them.

Without the hot and cold pixel removal:

With the pixel removal:

So, the cosmetic tab does the trick. I'd be happy with this, except that, as you can see above, it also seems to increase the overall brightness and noise of the image. I do not understand why. The above images were processed in precisely the same way, but the one with the hot pixels removed is definitely brighter.

I could probably live with this, but I'd rather have a more 'true' image to work with. As things stand, it seems that I either live with the hot pixels (which you can't really see anyway most of the time), or use the cosmetic feature and live with an image that seems to have been affected overall in some weird way.

Any ideas/comments/suggestions? I should add that I've tried and tested pretty much every other stacking solution and would very, very, very much prefer to stick with DSS.

Thanks, Brendan

Edited November 8, 2021 by BrendanC

[happy-kat]

The cosmetic tab leaving on hot pixel removal can also remove star centres, though no seen on your image, doesn't wipe clear the hot pixels up.

[BrendanC]

Sorry, don't quite follow - are you saying the cosmetic tab does work, or doesn't? 

I know what you mean about the star cores and have looked for that but not had that issue. 

What I'm most interested in is how to use the cosmetic feature without affecting the entire image so drastically.. 

[BrendanC]

I think I know what it is. A year or so ago, I went through all the different stacking modes in DSS and decided the Auto-adaptive one was best. So, I've been using that ever since. On a hunch, I went through them all again last night, and guess what? Average, Auto-adaptive, Entropy and Maximum modes seem not to handle hot pixels very well. Median, Kappa Sigma and Median Kappa Sigma handle them perfectly - no more hot pixels. It could still be that I need to dither more, because those modes might just be rejecting hot pixels that the darks haven't fixed. But it's an interesting finding.