de-logging

[bunk]

Yesterday I discovered something I kind of knew in the back of my head but never checked out.

I was doing a grade on the neutral grade I did earlier on the S-log3 footage Andrew was so kind to share with us. All looked fine, but the part of the couple near the
pedestrian crossing.
.The colours in the girls face felt apart. I reset the effect I was applying …and this time I only used the master curve, to get the two skin tones -which were falling apart- to match as close as possible. When I finished I had basically drawn a squeezed S-log3 curve.

Next I Googled for the biggest pictures I could find for S-log and V-log. I opened them in Photoshop and traced the curves. In a separate layer I created a square divided in 8 rows and columns, just like the background of my master curve looks like. Next selected the ‘traced curve’ and with the transformation tool forced the x-dimension inside the square. Flattened the image, imported it in my NLE and with three points recreated the curve in the master curve window. Bingo! Saved the the curve to an .acv format for later use.

….And that is al there is to de-logging a 1D-LUT or spline.  It’s easy to create, something you can do yourself.

So how does that work in practice. I can tell how I do it and think something alike should be possible in all NLE’s

I work in AE and use Color Finesse. I think it was at some point in time distributed for free with AE in the states. Not so in Europe, I had to pay the full price …but I really like the plugin and have no regrets.

The plugin is added as an effect to the footage. Under curves the ‘Log curve’ is loaded. Under Levels the input levels are adjusted (leave the grayscale handle as is, that’s why you created the LogCurve) and output if necessary. The changes are applied.

Brightness and contrast are now adjusted, no color adjustment is done. Basicly what the C300 gives as a preview option for it’s log.

Next an Adjustment layer is added to the timeline. ColorFinesse is applied to the Adjustment Layer and under HSL  Saturation under Shadow and Midtones is set from 100 to 133,33, Highlights left for what it is. My guess is that when 33,33 % saturation is added to each channel, you would get full Saturation. But that is just a guess.

You now have a ‘basic color corrected de-logged file’. To grade further let you imaginations go wild…

In the linked mov with Andrews footage I adjusted the curves like so. By banding the red curve downward you add a slight red cast to the footage as the curve to the top is no longer straight. Doing the opposite with green curve amplifies it. Blue curve is kept as straight as possible while adding blue to the shadows. HSL curves speak for themselves. Alas the girls skin still falls apart, so there must be something wrong with the footage

With above methode I’m less plagued by the YCbCr macro blocking on GH4 footage as with my other custom methode. Will have to do some more testing.
I thought I share my findings as maybe it’s of some use to others as it makes Log grading kind of simple.