Very interesting article.
My main complaint is that the author also did some other adjustments prior noise reduction, e.g. tone curve in the case of DxO. You can clearly see that the DxO processed image is brighter. Lens corrections were also applied.
I think it would have been better for comparability’s sake if she would have just tested the noise reduction without any other corrections. Also, 44% luminance may be a little high for my liking, and I rarely apply additional sharpness when already having the automatic lens sharpness switched on. In addition, value of 48% for chrominance seems too low, I checked with her original RAW file and there is plenty of colour noise left in the background which is by the way not just one colour or structureless but has some detail in it. By the way, why did she use a TIFF for working with Topaz? Everything is not very consistent.
HOWEVER, I have to agree that there are a couple of artifacts in the perimeter of the bird and a certain blockiness in comparison to TopazDeNoise is clearly noticeable. Topaz seems to render the image overall cleaner. But let‘s not forget that the zoom level is around 240%.
Otherwise, Topaz seems to lose detail in uniformly coloured areas if low light mode is used. Standard mode is not an option for night time images in my opinion. See for comparison the two following images, especially in the green circled area an in the black umbrella guy‘s grey jacket.
Topaz settings (first image): Low light mode enabled, Remove Noise 15, Sharpen 38, Recover Original Detail 100, Colour Noise Reduction 0
DxO settings: PRIME, Luminance 15 (my standard), Chrominance 50, Low Frequency 75, other settings 0.
Again, the DxO processed image seems to be quite tangling, especially in bigger uniformely coloured areas.
So, if PRIME is only 2nd best noise reduction, well… I really don‘t care that much. It is still one of the best. But I have to agree that people at DxO should not rest on their laurels but keep improvements going since there are still things to improve, e.g. look here.
The blockiness thing in addition is for sure a thing to keep working on.