We have reported continuously about getting your colours right when working with a not-so-perfect screen, the last time here. But what to do if you just want to connect hardware like a camera or player and you can’t trust your screen’s or projector’s colour fidelity? And what about connecting them if one has only SDI and the other side HDMI? Well, there is a solution that won’t cost a fortune.
Generating a LUT
The Spyder Pro can now optionally generate and export a LUT for screen corrections, not only ICC profiles. Sure, you’ll need a computer to run this process, as described here in full detail. The software still seems a bit flaky; sometimes it hangs when saving the LUT or makes a useless file with zero bytes or a few megabytes. After a few tries we got a LUT in the right size, which should be around 1 MB or less. Once you have saved that LUT in an appropriate size, you can load it into a simple interface or converter from your computer. After that, you don’t need your machine any more, only a small box.
The right device
Let’s say your source is delivering video by SDI, but you have made a LUT to correct colours and contrast on a screen or projector with only HDMI for input. The most flexible device at a decent price is the “Micro Converter BiDirectional SDI/HDMI 12G” by Blackmagic. What a mouthful! We’ll just call it the converter here, since it’s pretty small to fit such a name. It weighs only 150 grams, needs 4 W from any USB-C source and can be found for a street price from 150,- € upwards.
Its main advantage for this use case, apart from compatibility with all SDI sources up to 12G: it can take .cube LUTs in 33 point format. So, choose that size when exporting from the Spyder Pro software for a good balance between precision and compatibility. We have used Converter Setup version 12.2.1 without issues, but some users report they needed version 7.6.2 for other converters from that same line. Once the LUT is uploaded, you can choose if you want to apply it to only one output or both, which are always active on this model with any source.
Our results
We have tried this solution with a camera that had only SDI and also with SDI output from DaVinci Resolve via the UltraStudio Monitor 3G. Receiving devices were an older, relatively cheap LG monitor with UHD and a projector by LG with HD, both HDMI only. They were remarkably close with their specific LUT to the factory calibrated MacBook Pro M1 set to its preset for Rec.709 BT.1886. If anything, the Mac’s screen was a bit cooler and the others warmer. Not bad for a laptop from 2021 with factory calibration only.
Correction and a look?
Of course, you can’t see which LUT is currently loaded and which outputs are activated, since the small box has no screen or lights other than LEDs for power and active connections. Good old adhesive tape and, yikes, handwriting should help. You are free to load any 33 point LUT in .cube format, so it could also be a specific look you want to demonstrate.
The device will accept only one LUT, but if your screen is seriously off without the correction, why not combine the LUTs? DaVinci Resolve can do that even in the free version, but if you don’t have any such software, there is Colorizer.net which can do it online. You’ll need the membership, but it’s a humble single payment of 10,- € for a set of tools serving many more tasks around colour.
Alternatives
There are other LUT boxes by Blackmagic and other manufacturers, some cheaper and less flexible, some more expensive. But if you want to play out of a computer via HDMI, there’s enough software to do it. Professional NLEs can integrate a LUT for output, or a highly recommended commercial player called Screen by Videovillage, which handles RAW formats, and even the free IINA player will do for non-RAW (both Mac only). Since IINA is based on ffmpeg, you can also use a LUT by command lines.
