What Is a 3D LUT and How to Use One

If you’ve spent any time in photography or video forums, you’ve probably seen the term “LUT” thrown around. Film LUTs, cinematic LUTs, LUT packs for sale. But what actually is a LUT, and why should you care?

LUT stands for Look-Up Table

A LUT is a mathematical mapping that transforms one set of colors into another. Think of it as a recipe: for every possible input color, the LUT specifies what the output color should be.

A 3D LUT maps colors across three dimensions (red, green, blue) simultaneously. This means it can create complex color transformations that simple slider adjustments can’t achieve: it can push warm tones warmer while simultaneously cooling the shadows, shift greens toward teal while keeping skin tones natural, or emulate the specific chemical response of a particular film stock.

How a .cube file works

The most common LUT format is the .cube file. Inside, it’s just a text file with a grid of numbers:

LUT_3D_SIZE 33
0.0 0.0 0.0
0.0 0.0 0.05
0.0 0.0 0.12
...

Each line represents an output color (as red, green, blue values between 0 and 1) for a specific input color. A 33×33×33 LUT contains 35,937 color mappings. Colors between grid points are interpolated.

Where to get LUTs

Built-in film emulations

Spectral ships with 7 built-in LUTs that emulate classic film stocks. These are ready to use the moment you open a photo.

Film simulation recipes

Many Fujifilm photographers share their camera settings as “film recipes.” While these are camera-side settings, the resulting look can often be approximated with a LUT.

Custom LUTs

If you have .cube files from other tools or photographers, you can import them directly into Spectral. Just drag the file into the LUT section.

Using LUTs effectively

A common mistake is applying a LUT at full strength and calling it done. Here are some tips:

Dial back the intensity

Most LUTs are designed to show their effect clearly at 100%. In practice, 40-70% intensity often looks more natural. Spectral has an intensity slider for exactly this purpose.

Adjust exposure first

LUTs respond differently to bright versus dark images. Get your exposure roughly correct before applying a LUT.

Stack with fine adjustments

Apply your LUT first, then fine-tune with curves and HSL. Think of the LUT as the foundation and the sliders as refinement.

Export your own LUT

Here’s something unique about Spectral: you can export your current grade as a .cube LUT file. This means you can:

• Create a look in Spectral and use it in video editing software
• Share your exact color grade with other photographers
• Build a personal library of looks

Try it

Open a photo in Spectral, browse the built-in LUTs, and experiment with the intensity slider. You’ll understand the concept in about 30 seconds.

Open Spectral →