It is also incredibly resource-intensive and very slow so experimenting with different settings can take ages. I have not used it on my latest M1 machine so that may handle it better if it has been optimised for silicon Macs but they charge for regular upgrades so I am not intending to bother (my version is a few years old). The biggest problems I found with Topaz AI was that it produced strange coloured artifacts around the edges of slide mounts and even within the slides around objects when trying to deal with grain (not noise). I will try Topaz AI again when the occasion arises. I have used Topaz in the past way before ACR was any good. I may just not have tried hard enough or not the right way with Topaz. However this was trying to find a way to get rid of B/W grain in old negative scans. There was nothing I couldn't achieve with ACR. I've checked it against dfine and plain ACR. I'll DXO Pure Raw to see how it does, but I've not been that impressed with Prime Denoise previously. In spite of the above limitations, I still use V2.4.2 for slide processing but haven't updated in spite of frequent nag screens as the price isn't attractive enough for a minor upgrade. If it decides film grain = noise it will totally remove it, if not it may leave 'mottled' areas, so it takes a bit of tuning to see what works. So I tend to use Topaz on a duplicate layer and then blend at 50% with the original. I find that it can remove all noise (which then looks unnatural) and it tends to over-sharpen edges (even on the lowest sharpening setting). I also use Topaz on a separate layer so I can reduce the effect if needed. I therefore use the Topaz plugin within PS after conversion from RAW in ACR. In my experience Topaz Denoise AI doesn't work well on RAWs. grain in B&W negative scans or is that a no no? Also do either satisfactorily help in reducing p.m. I’m also interested in which application is the biggest resource hog, as I believe both use AI, as well as making the best job of minimising digital noise.

When I get a spare moment I’ll search for reviews.

Pure raw dxo