Flicker removal with expressions

[Pavel]

Hello everyone,

I’m rather new to Nuke, been working with it for a couple of month. I once had a scene where there was ambient flickering that was coming from TV. My initial thought was this: I could measure the intensity of some patch in the scene at the moment of lowest intensity. Then using CurveTools measure the changes in light intensity on that patch. And using this data I wanted to compensate for the flickering by subtracting values at the lowest intensity from the measured values at each frame and then reduce the gain in grade node by this amount.

Unfortunately I don’t know how to do something like this in Nuke. After searching around a bit I found this in one of the forums: r = r*(1/(CurveTool1.intensitydata.r)) *
(CurveTool2_SINGLE_REF_FRAME.intensitydata.r)

It might not be exactly the idea I had, but how do I actually implement this? Where do I need to put this to make things work. I would really appreciate it if someone could give me some explanation. Perhaps a link to some resource where I can read up on using expressions in detail?

Thanks for any help,

Pavel

[Author]

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