using of HSV Tool....

Hi,

This tutorial is about the using of HSV Tool and it is very useful when we have green screen behind a glass, window …and we try to save the reflection on them. ( key inside a car , refection on the window etc…)

We will start by importing the clip , in this case a single image. So – press R for read and choose the image.
I will add a Reformat node (image1) and then I was using 2 main nodes for soften the image – one is degrain simple – (image 2)in witch a modified the value for the green and blue channel and then the soften node - amount 0.83 ( just enough to get the transition between the color and green smoother as you can see in the image. 22)

Ok. The Clip (image is ready. I will add a HSV Tool now.
I will pick the scrcolor (screen color) green in this case, sample the green and turn the viewer window to alpha view.(image 3)

First thing I do is to press Invert mask. Second to go to HMask ( Hue Mask ) and turn it to rgba.green. image 4

Ok. Now it is time to add a BG so we don’t have to work blindly. The best it is to use the original BG but for control I am going to use the color bar.
I add a reformat node to it, same as the one that I use for the FG.
Then I will add a AddMix node and link the Fg to A and the BG to B.
Ready ….I will throw a viewer 1 to the Add Mix node and start working with the HSV Tool parameters. image 5
We want to save as much as we can from the reflections so I am going to add a second viewer to the FG reformat node- just for reference

In the same time I realize that if I am going to work like this, the result will be a blurred image and the best is to use a copy channel node as you can see in the image 6. This will help using the control for obtaining a proper alpha and avoid destroying the original. image 6

All right. Now everything is set up.

Looking through the viewer no 1, and having the HSV parameters open, I turn the min ( Hue, Sat) option on and I will start tweaking first the Hue range slide and then the range roloff until I will have saved the reflection.
Then I will tweak the same 2 knobs for the saturation until the level of reflection is nice. In fact, when I consider saving as much as I could from the window, I will stop.
In the same time, we can use the hue and brightness option instead of Hue, sat.
Depends on witch one is giving the best result.
But don’t forget to turn the Mask on .green. All that you use here has to have the mask turn on - rgba.green

Ok. Next I have to get ride of the green
I will add a Hue correct node and start alter the green in the green remove and the green in the sat option.



Finally I will arrange the 2 curves for the Add Mix node and turn on the premultiplied option.
For more or less level of dirt or reflection we can use a grade node before HSVTool and a blur (alpha channel) after just to smooth the surfaces.

image 7

In any case we can use a second key (hard) for fill up the holes and this one we can add to our comp using a channel merge node. Image 8


Here you have your nice key.




Hope this will help


Andreig



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