Particularly in PixInsight, which do people prefer?
DeBayerization: VNG or AHD?
Posted 14 February 2018 - 12:25 AM
I have the same question. Is there a good review of each and the pro's / con's?
You may want to post this in the PixInsight Forum.
- cobestluc likes this
Posted 14 February 2018 - 12:46 AM
It will be the best if someone can stack a bunch of raw images of reasonable quality with VNG and AHD, and compare them.
I had compared DSS Bayer drizzle, DSS AHD, Nebulosity VNG, PI VNG, and PI Bayer drizzle. For image sharpness and noise correlation between pixels, for a scale from 0 to 10, 0 being bilinear, and 10 being the best I have seen, I would rate as following:
DSS Bayer drizzle: 10
PI Bayer drizzle: 9.5
PI VNG: 9.0
Nebulosity VNG: 8.0
DSS AHD: 6.5
All of them are substantially better than bilinear. PI's VNG does remarkably well and can give results almost as good as Bayer drizzle, at least in my cases.
However, I have a feeling that PI's VNG is somewhat better than Nebulosity's VNG. So probably even with the same algorithm (VNG), different implementations can give you different results. Because of this, there is a possibility that PI's AHD is better than DSS's AHD. I can't tell since I have never tried AHD in PI.
Personally I use PI's VNG as default, and only switch to PI's Bayer drizzle when the images are taken under exceptionally good conditions and when I absolutely want the highest resolution. PI's VNG is much faster than its Bayer drizzle, and can give very good results.
Edited by whwang, 14 February 2018 - 12:46 AM.
- AbPho likes this
Posted 14 February 2018 - 05:39 PM
The background is that I have my own version of the PixInsight BatchPreprocessing script with a few functions added. I am wondering if I should put AHD on the menu (for some reason it is not there; VNG is the default).
Posted 14 February 2018 - 09:07 PM
Interesting. I had the impression that AHD is there, but when I open my PixInsight BPP, I do not see it either.
- MCovington likes this
Posted 15 February 2018 - 01:55 AM
It's definitely worth making AHD available.
However, I use bayer drizzle - it avoids artifacts in regions of high contrast - especially around stars.
Also, take a look at Juan's recent comments on the demosaicing in the libraw replacement for dcraw:
By the way, demosaicing is the word that PixInsight will using in future instead of debayer (which now has connotations of physically stripping the CFA layer off a sensor to make it monochrome).
Edited by sharkmelley, 15 February 2018 - 01:56 AM.
- MCovington likes this
Posted 15 February 2018 - 03:48 AM