What is a LUT's input color space?
If a LUT makes your footage look washed out, or crushed and oversaturated, the LUT is usually fine. It is being fed a different kind of image than it was built for.
A LUT is a table, not a filter that understands your footage
A 3D LUT (usually a .cube file) is a lookup table: for every input RGB value it stores an output RGB value. It has no idea whether the numbers coming in are from an iPhone in Apple Log, a DJI camera in D-Log M, or an ordinary video. It simply assumes a particular input, and that assumption is its input color space: a tone curve (how brightness is encoded) plus a gamut (which primaries the colors refer to).
When the footage matches that assumption, the LUT does what its author intended. When it does not, every value lands in the wrong place in the table.
The two kinds of LUT you will run into
| Expects | Typical names | What it does | |
|---|---|---|---|
| Conversion (technical) LUT | A specific log format | “Apple Log to Rec.709”, “D-Log M to Rec.709” | Turns log footage into normal-contrast Rec.709. Camera makers publish these. |
| Log look LUT | A specific log format | “Apple Log cinematic”, “for D-Log M” | A conversion and a creative look in one table. |
| Creative LUT | Rec.709 | Film emulation, “teal and orange”, most free LUT packs | Changes the look of footage that is already normal Rec.709. |
How a mismatch looks
- Rec.709 creative LUT on log footage: still flat and gray, just tinted. The LUT never received the contrast it expects.
- Log LUT on normal video: harsh contrast, crushed shadows, clipped highlights and loud saturation, because a contrast curve is applied on top of an image that already has one.
- Log LUT for the wrong log: for example an Apple Log LUT on D-Log M. Brightness and colors are both off, because the curves and gamuts differ. Even Apple Log and Apple Log 2 share a curve but not a gamut, so the colors shift (see grading Apple Log 2).
How to tell what a LUT expects
- Read the name and the description. “X to Rec.709” means X is the input. A LUT pack sold “for Apple Log” expects Apple Log footage.
- Try it on correctly exposed footage. If a LUT makes log footage look normal, it expects log. If it only looks right on footage that already looks normal, it expects Rec.709.
- When in doubt, assume Rec.709. Most creative LUTs are made for Rec.709, and converting log first is the safer order.
The right order for log footage
Colorists in DaVinci Resolve keep the conversion and the creative look separate and make their adjustments underneath:
- Log footage
- Exposure, white balance, contrast, wheels (under the LUT)
- Conversion to Rec.709, the camera maker's LUT
- Creative look (a Rec.709 LUT), at the strength you want
- Curves, secondary grading, texture
Importing a .cube LUT in Develop Log
Develop Log asks for the input space when you import, and places the LUT at the right point in the chain:
- In the editor, scroll the look strip to the end and tap Import LUT (Pro). Choose a
.cube3D LUT and give it a name. - Under The input this LUT expects, choose:
- Rec.709 for regular creative LUTs. On log footage the app first converts with Natural (the camera maker's official LUT), then applies yours. On regular video it is applied directly.
- Apple Log for LUTs that take log directly, such as “Apple Log to Rec.709” or Apple Log look packs. These appear only on log footage. Other log formats, including Apple Log 2 and D-Log M, are converted to the equivalent Apple Log first, so the LUT receives the input it expects.
- Pick the LUT on the strip and set its strength. Your adjustments keep working underneath it.
Save your own look. Once a grade is right, Save as Look (Pro) stores it on the strip. A saved look works on both log footage and regular video.
Quick answers
Does LUT size matter, 33 or 65 points?
A larger table follows the original transform more closely between points, but a well-made 33-point LUT is fine for most looks. Develop Log merges your LUT, the conversion and your adjustments into a single table that is looked up once per pixel, with 16-bit precision in between.
Can I apply a LUT for another camera's log?
Only if you convert your footage to that camera's log first. Matching the input space matters more than which LUT you pick.
Which LUT formats are supported?
3D LUTs in .cube format.