Apply a .cube LUT
A LUT is a colour grade stored as a lookup table: for every input colour, the output colour it becomes. Cinematographers and photographers trade them as .cube files, and applying one is how you get a consistent look across a whole set of images. Drop your photos and the .cube file together — the LUT is recognised by its extension.
Drop images and one .cube file
The .cube is detected automatically — multiple images allowed
What is actually in the file
A 3D .cube declares a size — 17, 33 and 65 are the common ones — and then lists that
many cubed RGB triplets as floating point numbers, with red varying fastest. A size-33 LUT is
35,937 entries. Since there are 16.7 million possible 8-bit colours, the table is a coarse grid and
the values between grid points have to be interpolated; this does it trilinearly, blending the
eight surrounding entries, which is the standard approach and what your grading software does too.
DOMAIN_MIN and DOMAIN_MAX are honoured if present. They matter for LUTs
built for log footage, where the input range is not 0–1. A 1D LUT_1D_SIZE file is also
accepted: that is three independent per-channel curves rather than a colour cube, so it can adjust
contrast and balance but cannot change hue relationships.
The intensity slider is the useful part
Most freely distributed LUTs are made for log or flat camera footage and are far too strong for an ordinary JPEG that already has contrast baked in. Applied at 100% they crush the shadows and shift the skin tones into something orange. At 30–50% the same LUT reads as a tasteful grade.
The blend is linear per channel between the original and the graded value, which is the same thing as a layer opacity in a compositing application. It is not colour-managed — everything here treats the image as plain sRGB, which is right for a web image and approximate for anything from a camera raw pipeline.
FAQ
It says the .cube file is short.
The declared size and the number of data rows disagree, which usually means a truncated download or a file that was edited. The message tells you how many entries were found against how many were expected — if it is close, the file lost its tail; if it is a fraction, the size line is probably wrong.
Can I use a .3dl, .look or .icc file?
No — only .cube. It is the most widely distributed format and the only one that is plain text and unambiguous. Most grading tools can export a .cube from the others.
Where do I get LUTs?
Camera manufacturers publish log-to-Rec.709 conversion LUTs for free, and there are large libraries of stylistic ones. Be sceptical about what a LUT was designed for: one made for S-Log3 footage will do something strange to a phone photo, regardless of how good the preview looked.
Does it handle transparency?
The alpha channel is untouched — only RGB goes through the table. A cut-out PNG keeps its edges exactly.
Can I build a LUT from a pair of before/after images?
Not here. That is LUT extraction rather than application, and doing it well needs many more sample points than a single image pair provides.