Topaz DeNoise 3.1.2 - Severe Noise Model - Do we have an Astrophotography solution now?

Looks interesting. In the previous versions of Topaz DeNoise, I always think it "creates" too much details that don't actually exist and sharpens the image too much. If the new version solves this, I will consider to use it.

@Kevin Morefield could you post a side-by-side comparison of the same image area? 
Certainly one can see the effect on the noise but I think one could give a better judgement if one can also observe the effects on the very same data.

Personally, I'd be totally fine the with quality of the noisy image as the noise seems to be free of any systematic pattern, spikes and isn't too intense.

Björn Arnold:
@Kevin Morefield could you post a side-by-side comparison of the same image area? 
Certainly one can see the effect on the noise but I think one could give a better judgement if one can also observe the effects on the very same data.

Personally, I'd be totally fine the with quality of the noisy image as the noise seems to be free of any systematic pattern, spikes and isn't too intense.

OK here are some crops of before and after.  This is RGB data, unprocessed except for ABE, a stretch and the aggressive vibrance and saturation to enhance the noise.

Here's some very fast testing. trying to upload as PNGs, so we'll see. 

1) Original, fairly noisy and stretched stack. (something with a very grainy background for testing)
2) "clear" mode in auto (high noise removal, low sharpness)
3) "low light" mode in auto (70,39)
4) "low light" mode, 70 denoise, 0 sharpening 
5) "severe" mode in auto (70,39)
6) "severe" mode, 70 denoise, 1 sharpening (lowest possible setting)

HH.zip

Björn Arnold:
In the Topaz image, the patchiness of the background becomes more prominent.

This is perhaps simply because the high frequency noise got removed?

Björn Arnold:

Yizhou Zhang:
This is perhaps simply because the high frequency noise got removed?

Yes, in deed. If the high frequency part is damped, you'll see the low frequency part more clearly. The patchiness is also there in the noisy image (just turn up the brightness of the screen and don't zoom in to see the whole image). The high frequency noise "distracts" from it. In the end, the balance matters. With some of the high frequency noise, one can have a more homogeneous background than without.

I agree.  I typically apply noise reduction like this with either a mask or opacity of about 80%  Leaving 20% of the noise seems to maintain the integrity of the image.

Olaf Fritsche:
I have never tried Topaz. But looking at the pictures above, I wonder wether the denoising is really better than the job Photoshop or Affinity Photo could do. How big is the difference?

if the Topaz model effectively behaves line a low pass filter then likely there won’t be a significant difference. The only and somehow major difference would be that one knows the behavior of a low pass filter, while the „AI“ model may produce unforeseen effects if it is applied to data which is inherently different than the training data upon which the Topaz model is built.

Kevin, thanks for posting this information.  I downloaded the latest version of Topaz AI and gave it a whirl.

"I typically apply noise reduction like this with either a mask or opacity of about 80%  Leaving 20% of the noise seems to maintain the integrity of the image."

That's exactly how I have used Topaz AI on a few of my images, except I use a 50/50 blend of Topaz and standard noise reduction to achieve a natural-looking result that is somewhat less noisy the the standard NR permits by itself.

Generally, I'm impressed with what Topaz can do for problematic noise in the sky background and the shadows of the images.  It's great for dark/dusty nebulae, maybe better than anything else out there?  However, I don't want Topaz touching my stars or the midtones/higlights of the image, where the S:N ratio is already good.  The ability to turn off the AI sharpening completely is huge to me.

I tried the newest version, and I found that the Severe Noise model with Sharpening = 0 still chews up the stars, but in a slightly different way.  In the Topaz GUI, the stars develop a slight pixelation effect that resembles under-sampling, and they are distorted around the edges after the image is saved.   I'm not sure it's an improvement over the previous versions.  The smaller stars are totally destroyed in the few images I tried processing.

Kevin, thanks for posting this information.  I downloaded the latest version of Topaz AI and gave it a whirl.

"I typically apply noise reduction like this with either a mask or opacity of about 80%  Leaving 20% of the noise seems to maintain the integrity of the image."

That's exactly how I have used Topaz AI on a few of my images, except I use a 50/50 blend of Topaz and standard noise reduction to achieve a natural-looking result that is somewhat less noisy the the standard NR permits by itself.

Generally, I'm impressed with what Topaz can do for problematic noise in the sky background and the shadows of the images.  It's great for dark/dusty nebulae, maybe better than anything else out there?  However, I don't want Topaz touching my stars or the midtones/higlights of the image, where the S:N ratio is already good.  The ability to turn off the AI sharpening completely is huge to me.

I tried the newest version, and I found that the Severe Noise model with Sharpening = 0 still chews up the stars, but in a slightly different way.  In the Topaz GUI, the stars develop a slight pixelation effect that resembles under-sampling, and they are distorted around the edges after the image is saved.   I'm not sure it's an improvement over the previous versions.  The smaller stars are totally destroyed in the few images I tried processing.

After the positive results with my NGC5566 data I tried the new model on M14.  There were no settings where the stars were not chewed to bits!   So clearly Topaz is not a solution for all images.   

As you mention, it doesn’t make sense to apply noise reduction to areas that contain sufficient signal sample to begin with.  So my normal approach is to is use a reversed luminance mask to apply noise reduction.   I usually adjust the mask to fully block stars and highlights and allow 80% to apply to the background.

Kevin,
I'm aware of Topaz but I've never used it.  You results look very nice but I'm curious how it compares with MureDenoise?

John

There is no reason not to apply MURE denoise as the first step of denoising. Even just a very light touch helps the image. Depending on how faint the target is, additional denoising applied to the linear image in PI (TGV or MLT denoise) may also be appropriate. Immediately after stretching the image is when I usually apply Topaz Denoise as non-linear denoising. I always remove stars before feeding the images to Topaz Denoise. Also, I use Topaz Denoise as a layer in Photoshop and then control opacity as well as masks if artifacts arise or if the effect is too strong. The stars can be added back either immediately or later with a Linear Dodge layer in Photoshop.