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Re: [OM] Another NR datapoint

Subject: Re: [OM] Another NR datapoint
From: Wayne Shumaker <om3ti@xxxxxxxx>
Date: Tue, 12 Nov 2019 05:16:26 -0800
The wall is a great shot. I do prefer Tina's original grainy version. It has 
more wabi-sabi. I hope she continues with her project, embracing any 
imperfection rather than rejecting it.

At 11/11/2019 08:29 PM, Moose wrote:
>When I saw Tina's photo of the Berlin Wall, I was interested in the noise. 
>This is in no way a comment on her decision to keep the noise - but it's such 
>an interesting case that I wanted to look into it.
>
>First of all, the noise in the sky increases the higher it goes. I don't know 
>if that is down to the film or to scanning software.
>
>I've been quite interested in Topaz Denoise AI. I've seen it perform miracles 
>- and fail.
>
>Here, it does a great job on the wall, the black coat, the monument/gate and 
>the lower part of the sky, but does almost nothing to the top. 
><http://www.moosemystic.net/Gallery/tech/Process/NR/Wallnoise.htm>
>
>I tried heavier settings, to little avail. So I tried creaky old Neatimage 4, 
>at settings that seriously blur detail, but clean up the sky nicely, and 
>applied it as a mask to sky only.

Non-comment noted...

I found that Denoise AI starts to fail when the noise becomes too much. As if 
it starts to think the noise is important detail and may even enhance it. With 
most digital noise, the noise is at the pixel level. Film has grain, noise can 
increase in size with grain. With my A7iii at ISO 3200, Denoise AI works great, 
but fails totally at ISO 65535. If you look close at the denoise AI version, 
the small grain noise is reduced in the sky.

I have one theory, although Denoise AI has AI in the name, the effect is almost 
as if it is doing an Inverse LCE (local contrast enhancement) at the pixel 
level. Hence its radius does not work with large noise, which requires larger 
radius which blurs the image. How is denoise AI to know what is detail and what 
is noise? It is only "artificially" smart.

WayneS - Information Theorist
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