Basic Resolve Grading Question

I just shot a short film using my original BM Pocket in raw.
I've edited the raw footage in Resolve 15.1
Most of the footage was well exposed, except some was over exposed a bit (Southern Italy!), and some had extremes, for example a bright sky with dark buildings in the foreground.
My problem:
When using a mask to adjust the gain in resolve, for example to pull down the sky a bit, or to pull up the building detail, I end up with patches of sparkling grains. Is this 'noise'?
How do I get rid of it?
I'm not trying to make large gain adjustments. My footage is raw, so I thought it could be manipulated quite heavily without having issues. Is it something I'm doing wrong in Resolve, or just a fact of life with extremes of light in a single image?
Everything in my grade looks great, apart from the odd sequence with these patches of moving grains.

Hey Chris
I'm guessing you might need to post an image or two so that folks can see what you're seeing, otherwise its guesswork ... but along those lines, it sounds like the patches of sparkling grain may be noise from a not great key (assuming your masks are qualifiers rather than power windows)? If so, you might want to try tweaking the Matte Finesse controls ... perhaps up the Denoise level a bit or add a little blur. If it's regular grain noise that's been heightened by gain adjustments though, perhaps a bit of targeted noise reduction will help.
Hope it helps
Andy

Thanks.
Yes, I mostly shoot short videos, close to the subject, indoors with lighting.
This is the first time I've tried to edit challenging daylight lit scenes in Resolve.
I am 90% certain I have my mattes set up badly then. I've tried moving the qualifier settings back and forth, adjusting all the matte finesse values. I fix one small patch and another patch becomes a problem.
It's guaranteed I don't know what I'm doing. It looks relatively easy and straightforward in all the tutorial videos online.
Still, as long as it looks like I have a problem with my matte settings, I can keep working on them, especially along the lines of what you have suggested.

Matte Finesse can be your friend. Don't forget there are TWO different pages of adjustments there, and it can get very fiddly. In some cases, two different nodes with different settings and a Key Mixer node could be used to do a complex key. (Key Mixer explained in Goat's Head tutorials on YouTube and in the manual.)

Matte Finesse can be your friend. Don't forget there are TWO different pages of adjustments there, and it can get very fiddly. In some cases, two different nodes with different settings and a Key Mixer node could be used to do a complex key. (Key Mixer explained in Goat's Head tutorials on YouTube and in the manual.)

This is very good advice. I've found sometimes you should create a new version and try pulling the matte again if you find yourself lost in the weeds, and if you still can't do it, you may have to make the adjustment over more than one node.

Thanks.
Still working on it. It's just two shots in my film. A darkish town with brighter dawn sky above.
I'm getting noise in both the sky and the townscape. Problem is some of the same colours are in the sky and town and some of the same luminance, dawn reflected in the white buildings. So it's proving hard to separate them. I may have to start again as suggested. I will watch again the tutorials.

Hey Chris
Don't forget you can target / limit the area for any correction, including qualifiers, by using power windows. Sounds like that might help in your situation.
Cheers
Andy

Yes, I was doing that too, but I think I'm going to initialise the grade of the noisey sequences and start again. It's only two shots in a five minute film.

Yes, I was doing that too, but I think I'm going to initialise the grade of the noisey sequences and start again. It's only two shots in a five minute film.

you can also try to start a new branch, heavy denoise the image, pull the key and pipe the key to the main branch.