CREATIVE LUTs


What is a LUT?

A LUT, a lookup table, transforms tone and color based upon settings chosen by the creator of the LUT. A LUT transforms incoming RGB data to your desired output values. Originally, LUTs were designed for practical purposes. A “Viewing LUT” would allow you to make log footage look like rec709 footage, so you had a better representation of what your final film would look like. “Calibrations LUTs” are used to calibrate monitor displays. There are “film emulation LUTs” that mimic the look of stock film. More recently, LUTs have been employed for creative purposes. (Creative LUTs).

In order for a LUT to be 100% precise the input has to match the conditions in which the LUT was created, likewise the output has to match 100% as well. You have to know exactly what your input device and output device will be. This is why LUTs are mainly used in-house at post-production houses or colorists working on their own stations.

If you’re using someone else’s LUTs you cannot be 100% sure what equipment they were using, and you also don’t know how they created this LUT.


HOW TO FIND OUT IF
A “CREATIVE LUT” IS BAD

It can be difficult to objectively judge the quality of a LUT being provided when applied to real footage. Here are two simple methods that help you to analyze a LUT.

1. Grayscale / Waveform test

A simple way is to place a grayscale image into your timeline and apply the LUT to it. In this example, you can already see heavy banding issues on the grayscale image itself. If you check the Waveform on the scopes, it reveals that the blacks doesn’t go down to zero. In the highlights the RGB values are “split” and the curve itself is a disaster.

2. Gradient / CIE chromaticity test

For this test, we apply a “four color gradient” to our timeline. It is pretty clear when you look at the gradient itself that you might run into artifacts, banding and noise issues. When we look at the ” CIE chromaticity” in our scopes, we see huge dark gaps between the colors.

For your information: The LUT with the weird grayscale curve comes from a very popular, successful and expensive LUT package. The company behind it calls themselves “Leading Developer” … and mentioned clients like Netflix, Sony and Universal on their page.

The other LUT is also a very popular and successful one. Some “LUT companies” claim to be “Industry standard” and write sentences like: “trusted and used by professionals” on their websites and mentioning clients like: ADIDAS, Lacoste and Gillette. But none of the LUTs I’ve testes so far are “professional”. More the opposite.


FOR COMPARISON

Rec709 Kodak 2383 D65 LUT by Blackmagic

Rec709 Kodak 2383 D65 LUT by Blackmagic


FURTHER INFORMATION


With this blog-post, I just want to show you a quick demonstration how to check LUTs easily with the tools inside DaVinci Resolve and sharpen your vision on LUTs.

Let’s summarize the most important points:

  • A LUT is always a “black box” / “mystery box”. You can not look inside a LUT and see how the LUT was build. You cannot “deconstruct” the elements.
  • You can only change the intensity of a LUT. So a LUT itself is not very flexible.
  • Use trustworthy LUTs only. It is always better to recreate a Look as a PowerGrade or hire a true LUT Developer for your project.


For more information on the topic “How to test LUTs“ I highly recommend this article from Jason Bowdach (PixelTools) for Mixing Lights:

Evaluating LUTs with a Stress Test:
mixinglight.com/color-grading-tutorials/evaluating-luts-with-a-stress-test/