What Is a .3dl LUT File and When Should You Use One?

When people talk about LUT files, they usually mean .cube. It's the format that DaVinci Resolve, Premiere Pro, Final Cut Pro, and Lightroom all support, and it's what most tutorials reference.

But there's a second format with a long history in professional colour work: .3dl. If you've encountered it in an Autodesk or Avid context and wondered what it is and when to use it, here's the answer.

What Is a 3D LUT?

Before getting into the formats: a 3D LUT (Look-Up Table) is a file that maps input RGB values to output RGB values across the full colour space. It's three-dimensional because it can represent changes that depend on the relationship between red, green, and blue channels — which is what colour grading actually does.

A 1D LUT can only apply tone changes uniformly across all channels. A 3D LUT can make a specific hue warmer in the shadows while leaving the highlights alone. That's why 3D LUTs are the standard for colour grading, as opposed to basic exposure correction.

Both .cube and .3dl store 3D LUTs. The difference is in the file structure, the supported grid sizes, and which software natively reads them.

The .cube Format

.cube was developed by Iridas (later acquired by Adobe) and is now the de facto standard in the broader video and photography industry. The format is well-documented, widely supported, and handles both 1D and 3D LUTs in the same specification.

Reads .cube natively:

• DaVinci Resolve
• Adobe Premiere Pro and After Effects
• Apple Final Cut Pro
• Adobe Lightroom Classic
• CapCut
• Most colour-managed apps and NLEs

A standard .cube LUT for colour grading is typically 17×17×17 (17pt) or 33×33×33 (33pt). The larger the grid, the more accurate the lookup — at the cost of file size.

The .3dl Format

.3dl is older — it originated with Kodak's colour science work and became widely used through Autodesk's colour grading and finishing tools. It covers a similar technical idea (a 3D colour lookup grid) but with a different file structure.

Reads .3dl natively:

• Autodesk Flame
• Autodesk Lustre
• Autodesk Smoke
• Avid editing systems
• Some broadcast and film finishing pipelines

The .3dl format stores the LUT as a flat list of integer RGB values rather than the floating-point triplets used by .cube. The grid starts from the minimum input value and steps uniformly through the colour space. It's a simpler structure in some ways — less header information, more direct.

One thing to know: there are multiple variants of .3dl in the wild. The Autodesk variant and the Kodak variant have slightly different structures. Most professional tools that claim to read .3dl are handling the Autodesk variant. When Luttie exports .3dl, it outputs the Autodesk-compatible variant — the one you'll encounter most often in broadcast and film workflows.

.cube vs .3dl: When to Use Each

The short version: use .cube for most workflows. Use .3dl when you're delivering to an Autodesk or Avid facility, or when a pipeline explicitly requires it.

Exporting .3dl from Luttie

Luttie exports both formats from the same grade. After you've built your look, click the export button in the editor sidebar. You can choose:

• Format: .cube or .3dl
• Size: 17pt or 33pt

You don't need to build separate grades for different formats. The same grade, exported twice, gives you both files — one for DaVinci Resolve workflows, one for Flame or Avid delivery.

You can also export a LUT pack — .cube files at 50%, 75%, and 100% intensity in a single zip — if you need flexibility in how strongly the look is applied.

What the File Looks Like

A standard .3dl file starts with a small header defining the input range and mesh size, followed by the table data as integer triplets:

3DMESH
Mesh 6 10
0 0 0
0 0 41
...
1023 1023 1023

The Mesh 6 10 line defines the input bit depth and the grid size. The table that follows lists the output RGB values for each point on the grid. If you open a .3dl file in a text editor, it's human-readable — which makes it useful when you need to inspect or troubleshoot a grade.

A Note on Accuracy

Both .cube and .3dl at 33pt offer enough grid points that the interpolation error between them is perceptually invisible for colour grading work. You'd only see meaningful accuracy differences at very small grid sizes (like 8pt), which aren't used in practice.

If someone tells you .3dl is more or less accurate than .cube, the format itself isn't the variable — the grid size is. A 33pt .3dl and a 33pt .cube of the same grade will render identically on any correctly-implemented LUT processor.

Summary

• .3dl is a 3D LUT format from Autodesk/Kodak lineage, widely used in broadcast and film finishing
• .cube is the standard for consumer and prosumer tools
• Both store the same type of data — a 3D colour lookup grid — with different file structures
• Choose based on your target software, not on technical quality
• Luttie exports both from the same grade at export time — no separate workflow needed

Open the editor and export your grade →

Related

• What is a LUT file?
• How to export a LUT from your color grade
• How to use LUTs in DaVinci Resolve