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LED Wall Virtual Sets

 
Author Steve

INF
Male
#1 | Posted: 17 Jun 2021 10:58 
Large, semicircle LED video walls are becoming the new choice for virtual backgrounds in the film & TV industry.
They are effectively replacing Green Screen shooting, as they give actors something to react to in real-time, and also create more realistic lighting on any reflective elements within the physical action.

But, one of the biggest issues facing the use of LED video walls is the way the camera 'sees' the colour emitted by the LED walls, compared to the live-action foreground elements.

Many companies that both supply LED video walls, as well as those that utilise them within their shooting, have adopted Colour Management tools from Light Illusion to ensure an accurate match between the foreground and background, in-camera.

A combination of ColourSpace, and suitable probes(s) is use for initial LED video wall calibration, with MatchLight the used to auto-generate a 'driving' LUT for the LED walls, to ensure the captured foreground and background images match.

This is yet another example of how far advanced Light Illusion colour tools are, compared to any other supplier.

Steve
Steve Shaw
Mob Boss at Light Illusion

Author Vassily
ZRO
#2 | Posted: 18 Jun 2021 12:51 
Hi Steve, what do you think about the following approach for LED video walls calibration.
1. Calibrate the LED video wall initially to any standard, let's say UHD Rec2020.
2. Calibrate reference LCD display to Rec709.
3. Output generated patches to LED video wall, capture them by Camera, output video signal from Camera to the reference LCD display, and measure the LCD screen by probe.
4. Create 3D profile on base of above setup and use it to generate 3D LUT for Rec709.
5. Use created LUT as the LED video wall calibration LUT.
Does this work?

Author Steve

INF
Male
#3 | Posted: 18 Jun 2021 13:06 
Hi Vassily
The issue is the camera doesn't capture Rec709 when being used in 'Log, etc' modes.
And the camera in-built Rec709 output is not a direct technical conversion from the 'Log' image - it has 'looks' embedded into the conversion.
And obviously Rec709 is a narrower gamut than the Video Walls.
That means the workflow will not be accurate.

But, you 'could' use 2 LCD Wall panels, both calibrated to a the same colour space, and feed the second with the output from the camera...
That 'may' work, if you have an accurate 'technical LUT' that converts the Camera output into the colour space of the LCD Wall panels?

Steve
Steve Shaw
Mob Boss at Light Illusion

Author Vassily
ZRO
#4 | Posted: 18 Jun 2021 13:29 
OK, got it. And what should we use in your example. Camera captured RAW Log images sequence as the "after" in MatchLight? And what is the "before", exported from ColourSpace (LightSpace) original calibration patches?

Author Steve

INF
Male
#5 | Posted: 18 Jun 2021 13:34 
No, you need a similar workflow, to make the output images map into the same colour space as the LED Walls are calibrated to.
So a technical conversion LUT before the images are loaded into MatchLight.

The key is the not clipping gamut or luma, as Rec709 would do.

Steve
Steve Shaw
Mob Boss at Light Illusion

Author Vassily
ZRO
#6 | Posted: 18 Jun 2021 13:38 
OK, thanks, that's clear now

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 LED Wall Virtual Sets

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