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Post #1072635

Author
lansing
Parent topic
Color matching and prediction: color correction tool v1.3 released!
Date created
3-May-2017, 11:54 AM

DrDre said:

lansing said:

DrDre said:

lansing said:

DrDre said:

It’s generally much faster to export a LUT for use in Davinci Resolve or Adobe After Effects, than to do it frame by frame in the tool. Shot-by-shot correction still takes a lot of time though, as each LUT is good for roughly 100 frames, and there are roughly 2,000 shots in a two hour film.

Thanks, I imported the generated LUT into Premiere and it applied instantly, with the cost of spike in RAM.

I’m testing it out on my dragon ball now, and I have a panning shot where there’re noticeable ringing artifacts along the lines. I have to turn smooth up to 0.9 in order to get it away. Is this normal? Can you take a look? I uploaded the reference and test image.

reference: http://i.imgur.com/id8AiRx.png
test: http://i.imgur.com/I54GI7O.png

Did you make sure the cropping is the same for the test and reference frames? If so, could you also share the raw test frame?

I tested on 3 other scenes, they all work fine even without cropping. I did try cropping this test image to match the reference, but it’s still the same problem with the white ringing between the character and the sky. I also tried sampling from the last frame of this same scene and it works fine again without the need to pump up the smoothing parameter.

reference: http://i.imgur.com/YOCkH0E.png
test: http://i.imgur.com/sRUrxNw.png

The fact that it works without cropping is fortunate, but the method is not developed specifically assuming the image content is exactly the same, except for the colors. It may work fine for some frames, but give artifacts for others.

The reason you get ringing is, because the ringing is already present in the test frame, a side effect of DNR:

The ringing has rougly the same color as the clouds next to it, both being light blue.

The clouds in the reference image are more white, than in the test frame, while the sky is a darker blue:

By color matching the color of the clouds, you automatically also give the ringing rougly the same color as the clouds, causing them to be more apparent against the darker blue background. Sadly there’s very little that can be done about this.

By increasing the smoothing parameter, you reduce the color gradients, as the algorithm tries to keep the gradients as close to the original gradients as possible, while also trying to find the best color match. This may reduce the ringing somewhat, but will generally also result in a poorer color match.

Thanks for the explanation, so I think the best approach for this is to find a frame in the scene that has the least amount of ringing + covers a wide variety of colors, build a matching model out of it and apply it to the entire scene and hope for the best.

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