Blackmagic Forum

Hi!

To properly understand my question please view the attached pic.

Let's say that is my scene. A woman in red lights. She turns her head so much that at some point we don't see her lenses in the frame.

I would like to select her left lens and turn it to blue while the rest of the image would unsaturated. Selecting the reds in her lens with a Qualifier is a no-go as it would select the rest of the pic because of color similarity.

What would be the proper Color Node structure for this task?

A- Selecting the left lens,

A- Making the rest of the clip unsaturated and leaving the lens red as it was,

B- Selecting the left lens again,

B- Changing the color of the left lens to blue?

Would I have to use two parallel nodes which both have the same selection using Window and manual Tracker (Frame). The first Node would do A task and the second would be inverted selection and does B task?

I hope you’re only using this as an example. If so, please excuse the following rant:

Shooting only* red light is a mistake that only makes postproduction more difficult. I’ve seen a few DPs do it just because they have access to some kind of colored LED... astra, Helios, whatever... It drives me nuts. You’re throwing away 2/3 of the information that’s hitting your sensor. Stop. You would literally be better off filming in black and white. If you want the image to be red in the end, it’s much easier to do *that* in post, and preserve the other channels for things like tracking, keying, or whatever.

In fact, the easiest way to get the effect you’re after would be to film an actress with blue lenses in full color, turn it all red in post, then selectively un-turn it red.

But if that’s all you’ve got and you can’t re-shoot it, you’re going to need to manually rotoscope the lenses. Resolve doesn’t have the strongest feature set for this. It *might* be possible, depending on the complexity of the shot (any motion blur, depth blur, hair, transparency, lens artifacts?), but other tools like Mocha pro would improve your odds.

So if it were me, and re-shooting wasn’t an option, I’d try to rotoscope in Mocha, import separate masks into resolve, and use those to change the color.

As far as layer nodes vs parallel, I don’t think it really matters as long as it works for whatever you’re trying to do. Test it first with simple shapes. Try the key mixer node to combine masks.

*and I really mean one narrow wavelength illuminating the entire scene. As soon as any other color enters the picture, you’re adding some kind of data to the green and blue photo receptors.


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Thank you, Jason. Shooting in red is something I will not do. I learned that from you.

The picture all in red is not my scene. It is just a picture from unsplash.com. I thought to use it as an example to ask how I separate reds.

My scene is the picture below. It also has three objects in red. I wanted only the cap to be red and the rest of the image unsaturated. But I failed doing that. I tried to do so in Balance node using Qualifier. Now I work with a compromise having all red objects saturated when the rest of the pic is not.

What I want to achieve I think would be possible with manual tracking the cap frame by frame but that's so much work that I don't think it is worth it in this artistic project.

Mocha looks like a real pro tool. I didn't understand if it is available for Resolve as an addon.

konstantin.nikkari wrote:What I want to achieve I think would be possible with manual tracking the cap frame by frame but that's so much work that I don't think it is worth it in this artistic project.

The automatic tracking can work to a point. I would qualify that red cap, draw a shape around it, track it automatically, and then go into manual mode and touch up the tracking where necessary. In some cases, you have no choice but to track it a frame (or a few frames) at a time, or whenever the actor moves. Generally, that's only a few shots here or there, but if it were dozens and dozens of shots, that could be a drag.

Bear in mind the shape can be fairly loose if it's just tracking a qualified key, assuming a similar color doesn't get directly in front or in back of the actor.

After a long fight I managed to do this with three parallel nodes. Thanks for help! I don't know if my way was the shortest but at least I got there where I wanted to.

Node 1
Target everything inside Window but the cap

****Node 2
****Target all reds outside the Window -> desat reds

Node 3
Target everything outside Window -> desat

EDIT!!!

And while I was writing this post I found out that it is possible to achieve with just two Nodes. See the picture attached.

The OFX version of Mocha Pro did work in Resolve last time I checked, but it always worked better for me in Fusion standalone.


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