Shading Cinema-Broadcast cameras with LUT profiles

Shading Cinema-Broadcast cameras with LUT profiles

Tags
Production

A Sony FX6 Full Frame Cinema Camera outputting SLog-3 via SDI
A Sony FX6 Full Frame Cinema Camera outputting SLog-3 via SDI

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The Ross Carbonite Ultra Switcher added support for SLog-3 dynamic range in version 6.6.0. This wasn’t an option when this post was written (but probably wouldn’t have changed the techniques used to accomplish the end goal).

Early on when conceptualizing an upgraded camera package we decided to record in SLog to retain far greater control over the final image when bringing it into a post-production workflow. This posed some challenges to a traditional broadcast workflow which typically operates in the REC.709 colorspace and content going externally (distributed in the building or to the web) needed to conform to broadcast video and color standards.

In order to capture in SLog we need to output the raw log sensor data directly out of the camera’s SDI output (or HDMI output in some cases) and later down the signal chain convert it to broadcast REC.709 colorspace. To do this we set our cameras to all output SLog-3 and send their output into our video router– allowing us to route the raw camera output to any destination on the router (including our record decks). Once the video signal is passed into the router, we need to apply a Ciné-grade Color Lookup Table (LUT) to the footage to bring it up to broadcast levels– shading the cameras also needs to happen with a very low latency (~1 frame or less)... to do this I looked a many hardware solutions including AJA Lut-box, AJA FS-HDR, BoxIO Lite SDI and many others but the price pre-channel of video was incredibly cost prohibitive to the budget we were working with. (Least expensive list price was $185.00/channel, with the more expensive options being several thousands of dollars).

I had an epiphany when I realized that due to the pandemic many film studios were liquidating their gear and selling at a much lower price point. I was able to find a seller on eBay who was selling Blackmagic Design SDI to HDMI 6G Mini Converters which have the ability to load a color lookup table (LUT) via USB into the converter and then output the shaded look via HDMI (and also SDI passthrough– which is what we actually want as our facility runs on an SDI backbone). Each input and output from these converters can be put on a router and then any source can be shaded by routing it through the “shader” device.

Signal Flow

Camera → Router → Blackmagic Design SDI to HDMI 6G Mini Converter → Router → Switcher Frame → Output to Encoder