It depends on your LUT.  If it's a 3D LUT, then it can not be inverted in general. 1D LUTs can often be inverted.  LUT Buddy has an invert button that will be enabled when the LUT is invertible.

In the 3D LUT case, imagine you had a LUT that was used to turn your image black and white (desaturate).  As you know, no color operation could hope to magically restore the color once it had been taken out.  So that's a clue as to why 3D LUTs can't generally be inverted.

If you created your 3D LUT using a series color corrections, your best hope is to try to apply them in reverse with inverted settings.  You could then make a LUT of that operation to be your inverted LUT.

But usually you just try to come up with something close or deal with it on a case-by-case basis.


Brendan

On Feb 2, 2012, at 11:09 AM, Byron Nash wrote:

> I was wondering if there is a way to inverse a LUT? I'm applying an Arri Alexa LUT to some footage for VFX work. Some of the elements are graphics that need to maintain their color with and without the LUT. We have been using a LUT on an adjustment layer and then turning it off before rendering it. That way our VFX should be in the correct ranges for Color Correction. This works fine for source footage but as soon as you need to put a logo in there it gets weird. I'd like to be able to put a reverse of the LUT on the logo/graphics and keep all that under the Adjustment layer.  In the past we have just sort of used levels and curves to approximate the graphics with some success. But I'd like to do it the "right" way.

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