Tips for making an awesome in-camera LUT for livestreaming

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skirsch

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  • Joined: Wed Nov 09, 2022 10:59 pm
  • Real Name: Steven Kirsch

Tips for making an awesome in-camera LUT for livestreaming

PostWed Nov 23, 2022 7:40 pm

I'm not a professional video expert, but just an engineer and CEO of multiple high tech companies.

However, I do want to look good on a livestream.

So I bought a BMPCC 4K and an ATEM Mini to interface it to vMix which is a godsend since it has all the scopes you need. I love being able to tweak the camera settings in the ATEM desktop app and saving the settings as a macro.

I was very disappointed with the LUT to Rec 709 that came with the camera.

After much fiddling, I got awesome results by making a custom LUT.

Here are the things I learned to help the next newbie:

1. Even though you are streaming 1K, you have to record in Film in at least 2K resolution to get the full frame.
2. When you make the LUT in Davinci, you only need 2 nodes: one for the color checker match, followed by a curve to lift the skin tones. Always use a video color checker card (it's cheaper than the video passport). It turns out, my face tone is NOT on the skin hue line. I was thinking it was a bad match all this time because I was using a Color Checker Passport which doesn't have the skin tones.
3. The adjustment node is simple using curves (the main screen). Pick a spot on the face which gives you control points on the line and lift the point so you raise up the red in your face to around 896 in the RGB Parade scope. This is so your face will be bright on camera. Otherwise, you'll typically be too dark compared to your guests. You should only have to move up the control point it gives you just a little bit
curves modification.JPG
curves modification.JPG (41.13 KiB) Viewed 719 times

4. Always set your WB in the camera using AWB off a grey card. Using scopes on the monitor output to set the white balance is a big mistake because the LUT can shift the WB (which I had never thought about before). I checked it in davinci and didn't think I needed a corrector node so i was surprised by this.
5. I added a third node to boost the saturation to 55 from 50 so that my minimum saturation in my face was 4 or more.

This process takes less than a minute (now that I know the process).

Then you can do any final tweaks in the ATEM if needed (like LIFT -0.02 in my case).

The results were impressive. I have a P4K2Alex LUT which includes in-camera LUT for the BMPCC and this custom LUT is better in my non-expert opinion.

My lights were Elgato Key Light Airs set to 6100 which gives a color temp of around 5280 according to the Sekonic). I wanted to create the custom LUT because all the LED lights (from pretty much everyone) have an SSI compared to D55 of around 70% (nobody shows you the spectral curve of these lights which I learned from my Sekonic C-800 light meter is pretty surprising especially the blue peak)

I hope this is useful to the next newbie.

LUT 21.2 Lift -.02 with waveform.JPG
This is the image
LUT 21.2 Lift -.02 with waveform.JPG (170.92 KiB) Viewed 825 times

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