Blackmagic Forum

I see some folks put an NR node at the very beginning of the node tree and others put it almost last - Does it matter where the node is placed?

I think there’s the same question on another thread. I used to add at the end of my nodes, but now NR is my first working node however it has no content until I finish my edit and grade. After thinking about it, the other later nodes should have an easier task starting with a relatively clean slate. Because there’s no content, initially, for edit/grade, I really rely on judging the deliverable for quality which always needs to be scrutinized anyway.

This is a religious decision. There are people who will tell you that you are wrong no matter which way you choose.

It has been discussed a million times and you can find those discussions here and on reddit to review pros/cons of each.

I tried to do a test of what is 'better' here;
https://www.reddit.com/r/davinciresolve/comments/10grsi2/does_color_space_of_nr_affect_outcome_vmaf/
But ultimately all I could show was it was different, but not better or worse.


Big advantage to first is that the NR will cache and will not need to re-calculate with each change you make downstream. But if your machine is powerful enough and can render NR in real time, this is irrelevant.

My thought is if I am trying to remove color noise (which is way more offensive to me than luma noise) then I want to do that before all my adjustments add saturation and change hues.

I have seen argument that at the end is best because you have increased the contrast for the NR to better be able to 'find' the noise. Neat has you tell it if the node is in flat log space or contrast rec709, so it apparently doesn't need the 'help'?


I would hope we all agree don't go cranking NR to the max as the first step, regardless of it the node is first or last. Dial in you grade then chose the bare minimum NR you need to get an acceptable image.

bwalker28277 wrote:Does it matter where the node is placed?

It makes a difference. Of course, it would.

Is one "more correct"? I won't go that far.

How far would you dare to go to then ?

I favor putting it at the end, so that it works on the noise profile that exists after I do the color work.

Is that the best option for every clip, every project?

Ask Marc.

I was kidding, but since you answer pretty seriously, what I'm into leads me to put it in the beginning, so that any matte involved later won't have dancing edges... I admit it's connected to dealing with mattes and won't suit anybody.

Is that the best option for every clip, every project?
Ask Marc.

Actually I used to ask Walter in those cases...

As for the correct luma and chroma values to do a reasonable noise reduction, you can ask Resolve for guidance based on the Analyze option in the Noise Reduction panel on the Colour Page. It gives a very precise answer based on the current position in the clip. I use that as a guideline when a particular area of the clip may be sensitive to the amount of noise. You can select less strength than Resolve suggests. Nobody wants to render plastic, but you don’t want a snowstorm either.

I'm a fan of placing it early for three reasons:

- node caching: improving playback performance
- easier job with qualifiers and tracking power windows, because the noise would disturb those
- consistency: noise at 800 ISO is usually always the same intensity. but grading might be different. reducing noise later would require drastically different settings in each shot even though the ISO stays the same

I do however also see benefits of placing NR last

Sam Steti wrote:Actually I used to ask Walter in those cases...

That works.

Sven H wrote:I'm a fan of placing it early for three reasons:

- node caching: improving playback performance

There's a new way to handle this which I've been using. If we use Node Stacks, we can place the NR either in an early or late stack, and then Disable that Stack for performance, turning it back on just before export.

Sven H wrote:reducing noise later would require drastically different settings in each shot

Exactly.

My preference is
1) node with main contrast for the shot
2) NR
3) everything else

Well see here, we’re all wrong! It’s not first and it’s not last. Walter I can try this approach on my next shoot.

Sven H wrote:I'm a fan of placing it early for three reasons:

- node caching: improving playback performance
- easier job with qualifiers and tracking power windows, because the noise would disturb those
- consistency: noise at 800 ISO is usually always the same intensity. but grading might be different. reducing noise later would require drastically different settings in each shot even though the ISO stays the same

... and reason #4: I'm theorizing that when one "amplifies the signal" (grades the shot) that has noise in it then one will amplify the noise too making overall final quality of the signal worse, and in turn grading harder to judge, than it would be if the noise was eliminated before signal was amplified.

bwalker28277 wrote:I see some folks put an NR node at the very beginning of the node tree and others put it almost last - Does it matter where the node is placed?

I generally tell my students that when it comes to Resolve Noise Reduction (NR), LESS IS MORE. There's always a price to pay with NR, usually loss of detail.

A few general tips:

I generally tell my students, I'm opposed to putting NR in the very first node because you're trashing the signal before any contrast adjustments are made.

To me, you're much better off doing color management, adding the required contrast change, then altering the color as required for each shot... and THEN (and only then) adding NR if it's needed. Otherwise, if you're trying to apply NR to a low-contrast Log signal, the overall effect is going to be unpredictable. I also believe it's important to make shot-specific adjustments to NR, and also to use different amounts of Y NR and C NR depending on the nature of the shot.

I get that people are unwilling to apply NR later on in the node tree because they want to cache it all. My take is, if you have to do that, put the NR in the middle of your node tree and cache it there if you need to. Now, if you need to make further trims, do it in additional nodes after that point, and it won't have to be re-cached if a change is made.

Me personally, I think there's much too much noise reduction going on out there. Noise is not inherently bad -- some noise is expected, even necessary, because it exists in life and in photography. The possible exception would maybe be for a beauty project (like a Maybellene Commercial), where it would have to be scrupulously clean and beautiful from start to finish. But not everything has to be that way.

Thanks for all the suggestions, Marc. I’m currently rendering a revised ProRes 4K video now with NR in the middle. Up until this thread, I always had NR as my last node, but there have been a few arguments in this thread that leaving it last may have the noise altering the adjustments in the earlier nodes. I agree less is more and each scene potentially will have differing needs.

I tried the Ultra setting once in a difficult situation and fortunately it cleaned up a scene that had failed miserably when only using Enhanced (my regular setting). Thank goodness for the availability of Ultra just before I did a previous video with smoke causing a rendering disaster until Ultra made it look perfectly as intended.

waltervolpatto wrote:My preference is
1) node with main contrast for the shot
2) NR
3) everything else

Yeah, this is the way most people I know work (including me). Makes perfect sense.

I get there are people who struggle with getting NR to run at speed and need to cache. But I think you can set it up to use NR in the middle of the node tree and still do trims after that, and not have to re-cache.

Marc Wielage wrote:To me, you're much better off doing color management, adding the required contrast change, then altering the color as required for each shot... and THEN (and only then) adding NR if it's needed.

That's the approach I generally use.

Okay, I’m just going with the primary colour adjustment after NR today as I thought that was the message yesterday, but that will wrap post for last weekend’s shoot.

The next shoot will have raw temp/tint adjustments, contrast, colour, adjustments and then NR followed by the final group of nodes.