Splitter Combiner node to modify color in key

Hi,

I've isolated the sky in a shot using the 3D qualifier, and wish to modify its color to a specific RBG value. Isolating each channel using a splitter combiner node does this efficiently, as I simply pull down the gain of the individual R, G, B nodes to get the exact color I want.

The problem is, I don't know how to use the splitter combiner node to affect only what I've qualified with my key. Using the RGB mixer within my 'sky-key' node to change the color to a specific RGB value is really hit-and-miss; I pull one channel down, and the others go up, etc.

So if anyone can clue me in on how I might be able to use the splitter-combiner node or another means that allows the same precise control over RGB values to affect my key, I will be very grateful.

Thanks in advance,
Monk

NODE TREE w/PARALLEL MIXER NODE

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I think you're trying to do this in an extremely complicated way. You might find you get much faster results keeping things very simple. The splitter-combiner is useful for some things, but it's not what I'd pull out for a situation like this.

I frequently pull a key on skies just by qualifying the highlights, tracking a shape on just the sky so that nothing else is affected, keeping the key soft (and with some NR if possible) to minimize any "choppiness," and then very subtly lean it in the direction I want with Primary gain. Sometimes multiple shapes are necessary if I want to keep the clouds white. Anything more than that, I'll go for sky replacement provided there's time and money to do so.

The problem is, I don't know how to use the splitter combiner node to affect only what I've qualified with my key.

Not an expert, so can't comment on the method, but given the tree you have I think you just need to pipe the key output (the blue dot) from your sky key node to the key inputs on your split nodes.

I frequently pull a key on skies just by qualifying the highlights, tracking a shape on just the sky so that nothing else is affected, keeping the key soft (and with some NR if possible) to minimize any "choppiness," and then very subtly lean it in the direction I want with Primary gain. Sometimes multiple shapes are necessary if I want to keep the clouds white.

Hi Marc,
Thank you for offering your expertise to help me out. I'm not having a problem qualifying my key however. I pulled a great key for the sky, but I'm now trying to change the color of the sky around to a specific hue (115,150,115) that I picked from a reference image. I'm all for simplicity and efficiency as well, but can't seem to find a way to change my sky to a specific RGB value. I tried using the offset wheels and RGB mixer but they're not efficient to get to a specific value. It's just random hit-and-miss with them.

So what method might you recommend to get the sky I've keyed to a specific RGB value?

Thanks again!
Monk

The problem is, I don't know how to use the splitter combiner node to affect only what I've qualified with my key.

Not an expert, so can't comment on the method, but given the tree you have I think you just need to pipe the key output (the blue dot) from your sky key node to the key inputs on your split nodes.

Hey Andy. You're obviously far more an expert than I am, as I did what you suggested and I'm obviously on to something! But when I decrease the gain on the blue channel, instead of affecting the sky that I've keyed, it's affecting everything OUTSIDE of my key, and keeping the sky as it is. What might I be doing wrong?

Thanks again!
Monk

I pulled down the gain in the blue channel,and instead of affecting the sky that I keyed, it did everything OUTSIDE of the key.

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Hey Monk
Yep, just tried and sure enough the key seems to get inverted, not sure why (hence not an expert!) but you could always invert the key, either in the sky key node or in the split node(s) where you're making the gain adjustment(s), and that should get things back where they need to be.
Andy

Hey Andy,
That did it! I inverted the key as you suggested, and it allowed me to use the individual RBG nodes in the splitter-combiner to modify the region in my key. Not sure why it's behaving like that (hence not an expert), but it worked. I'm kind of excited about using the splitter-combiner in this manner to more precisely change hue.

Thanks again! I wouldn't have left my workstation until this was solved. I'm now free.
Monk

you're making it way too complex

1) if you look at the rgb mixer, you will notice that there is a "preserve luminance" button. tick that off and you will get what you want.
2) if you put "luma mix" at 0 (in primaries), now the RGB gains are independent to each other, so you can use that as well to acheive the exact same result.
3) if the "key" is inverted, in the "key tool" there is a convenient "invert" button
4) all those operations can be done in one node

keep it simple.
and all those little things are covered in the manual if you need more references..

Between "Sky node" and Splitter Combiner add Outside node and connect its alpha output with alpha inputs of Splitter nodes.

another somewhat simpler option would be to key sky as needed, add color compressor OFX, type in the rgb values needed and run the hue slider up, and blend down untill happy

i've used this on commericals where the cleint was needing precise values on many objects includeing the sky

the product's hero colors were sky blue and orange, so we needed the sky, hero's shoes, watchband, charge card etc to match the logo's sky blue - and the orange car, suitcase, flowers, actor's tie etc etc to match the logo's orange

color compressor is a huge help for this, does what you seem to need well, and is much simpler than the mess of nodes on screen cap...

color compressor is a huge help for this, does what you seem to need well, and is much simpler than the mess of nodes on screen cap...

I agree, OFX Color Compressor can be a miracle worker under the right conditions.

1) if you look at the rgb mixer, you will notice that there is a "preserve luminance" button. tick that off and you will get what you want.
2) if you put "luma mix" at 0 (in primaries), now the RGB gains are independent to each other, so you can use that as well to acheive the exact same result.
3) if the "key" is inverted, in the "key tool" there is a convenient "invert" button
4) all those operations can be done in one node

Thank you! Excellent answers... 'Preserve luminance' in RGB mixer (page 1955 in Resolve 15 manual), and 'lum mix' (page 1945) in primaries allowed me to precisely achieve the desired RGB value. It's helpful to know the myriad of ways to accomplish this, thanks to your and everybody else's super-constructive input. I really appreciate you taking the time during the weekend to share your knowledge.

Thanks again,
Monk

another somewhat simpler option would be to key sky as needed, add color compressor OFX, type in the rgb values needed and run the hue slider up, and blend down until happy

Hey Dermot,
Perfect! This is the fastest, most precise option suggested yet! Thank you immensely.
I've been reluctant to wading too deep into the creative waters of secondary corrections but I learned so much thanks to you, Marc, Andy, Walter, and Vit. It's really rewarding to learn from all of you - wonderful community here.

Thanks again,
Monk