You just downloaded a LUT pack. There are 30 presets, they all have cryptic names like CIN_D65_WARM_v3.cube, and you have no idea which one to use - or whether any of them will actually do what you need. The conventional approach is to apply each one to your footage and scrub through until something looks right. That works. But there is a faster and considerably more informed way.
A LUT analyzer lets you read what a LUT actually does before you apply it: its contrast curve, colour temperature bias, saturation response, and clipping behaviour. Once you know how to read these signals, selecting the right LUT takes seconds rather than minutes - and you stop making grading decisions by feel alone.
This guide walks through the free LUT Cube Analyzer at alestemple.net - a fully browser-based tool that works with any standard .cube file, runs entirely on your device, and requires no account or software installation. It covers all six analysis tabs and ends with a practical 60-second evaluation workflow you can start using immediately.
LUT Cube Analyzer - six analysis tabs visible after loading a .cube file: 3D Cube, Curves, Preview, Scopes, LUT DNA, and Compare.
What Is a .cube LUT File?
A .cube file is the industry-standard container for 3D Look-Up Tables. It stores a three-dimensional colour remapping grid: for every possible combination of Red, Green, and Blue input values at a given resolution (typically 33 grid points per axis), it specifies the output RGB values the NLE or colour grading software should produce.
The format is used by virtually every professional tool: DaVinci Resolve, Vegas Pro, Adobe Premiere Pro, Final Cut Pro X, After Effects, Lightroom, Capture One, and Photoshop all read .cube files natively. When someone says “here is a LUT for my preset pack”, they almost always mean a .cube file.
A standard 33-point .cube LUT contains 35,937 colour samples (33³) - each one a precise RGB→RGB mapping instruction. A 65-point LUT contains 274,625 samples - nearly 8× more data points. Yet both files describe the same creative look; the higher resolution simply reduces interpolation error between sample points, producing smoother gradients and more accurate skin tone rendering. The difference matters most in banding-prone scenes such as blue skies, soft out-of-focus backgrounds, and smooth skin. Here is the revealing part: DaVinci Resolve has supported 65-point LUT generation in its professional colour pipeline for many years, making it the long-standing standard in high-end post-production. VEGAS Pro 23, on the other hand, only introduced native 65-point export relatively recently - which means that for the majority of editors working outside a Resolve-based pipeline, most of the LUTs in their collection are almost certainly still 33-point files.
Step 1 - Open the Analyzer and Load Your LUT
Go to alestemple.net/tools/lut-analyzer.html. No installation required - the tool runs entirely in your browser using WebGL and the Web Workers API. It works in Chrome, Edge, Firefox, and Safari on any modern desktop.
Drag and drop your .cube file
Drag any .cube file directly onto the drop zone, or click Browse Files to open the file picker. The tool supports grid sizes from 17³ to 65³ and files up to 9 MB. Parsing runs in a background worker - the page stays fully responsive even for large 65-point LUTs.
Wait roughly one second
The LUT is parsed, validated, and all six analysis modules run simultaneously. For a standard 33-point LUT this completes in under 500 ms. A loading indicator appears during processing. If the file is malformed or uses an unsupported grid size, an error message appears.
Explore the six analysis tabs
Once loaded, six tabs become active: 3D Cube, Curves, Preview, Scopes, LUT DNA, and Compare. Each tab answers a different question about the LUT. The remainder of this guide takes you through each one.
Privacy: Your .cube file never leaves your device. All analysis runs locally in your browser using JavaScript and WebGL. There is no server upload, no file storage, no account required. The privacy badge at the top of the tool confirms this.
Tab 1 - 3D Cube: The LUT’s Spatial Fingerprint
The 3D Cube tab renders the LUT’s colour transformation as an interactive point cloud in a 3D RGB colour space. Each of the LUT’s grid points is plotted according to its output colour value. An untransformed identity LUT produces a perfect, evenly distributed cube. A creative LUT distorts, stretches, rotates, and compresses that cube in ways that directly correspond to its colour behaviour.
3D Cube tab - point cloud in Heatmap encoding. A cluster shift toward warm tones and slight shadow lift are immediately visible in the spatial distribution.
3D Cube
What to look for
Points mode shows the output positions of each grid node. Vectors mode draws arrows from the neutral-identity position to the actual output - the longer the arrow, the stronger the transformation at that node. Lattice mode connects neighbouring grid points with lines, making global warps and local distortions immediately visible. Use the Zone filter to isolate Shadows, Midtones, or Highlights. Rotate freely with the mouse or enable Auto-Rotate for a full 360° view. The Clip Overlay highlights nodes that exceed the 0-1 output boundary in red.
What to read at a glance: A uniform expansion away from centre = global saturation increase. A vertical translation of the shadow cluster = black lift or crush. A skew toward a warm corner = colour temperature push. Corners pushed outside the cube boundary = output clipping that will burn highlights or crush shadows on real footage.
Tab 2 - Curves: Tonal Behaviour Per Channel
The Curves tab samples the LUT along the neutral axis (R=G=B) and plots the per-channel response curves for Red, Green, and Blue independently. This is the fastest way to read the LUT’s tonal contract: where it adds contrast, where it lifts the blacks, and whether it introduces a colour temperature shift in specific tonal zones.
Curves tab - per-channel R, G, B tone response curves. The hover tooltip shows exact input→output values and deviation from the identity diagonal at any point.
Curves
What to look for
Hover anywhere on the canvas to read the exact input level, per-channel output, and deviation from the identity line. An S-curve shape = contrast boost; steeper S = more aggressive compression in shadows and highlights. A flattened curve = log-style roll-off or low-contrast treatment. When the R and B channels diverge significantly, the LUT introduces a colour temperature shift - Red above Blue in the highlights = warm highlights; Blue above Red in the shadows = cool shadows. The grey dashed diagonal is the identity reference line.
Tab 3 - Preview: Before / After on Your Own Image
The Preview tab renders a live before/after split view. You can evaluate the LUT against the built-in synthetic test layers (Hue Matrix, Grey Ramp, Skin Tone patches, Banding Test) or - and this is the most useful option - upload your own JPEG, PNG, or WebP image to see exactly how the LUT performs on real footage from your actual project.
Preview tab - draggable split view with a user-uploaded frame. Left: original. Right: LUT applied. The image is processed 100% in-browser and never transmitted anywhere.
Preview
What to look for
Drag the split divider slowly across skin tones, neutral grey areas, and deep shadows. These zones reveal the LUT’s colour temperature bias, shadow lift behaviour, and black-point treatment far more clearly than saturated colour regions. For the most accurate evaluation, upload a representative still frame exported directly from your NLE timeline - the same colour space and exposure as the footage you will actually be grading. Files up to 20 MB are supported.
Tip: The Hue Matrix synthetic layer sweeps the full 0-360° hue range at multiple luminance levels. It is the fastest way to spot hue rotation artefacts - situations where the LUT shifts a specific hue (e.g. sky blues or foliage greens) in a direction you do not want. Combine it with the Skin Tones layer to verify the LUT’s treatment of the most colour-critical region in any human subject footage.
Tab 4 - Scopes: Broadcast-Grade Signal Analysis
The Scopes tab runs the LUT through a 32³ test signal (32,768 unique RGB combinations covering the full colour cube) and renders five professional broadcast scopes. This gives you the same analytical depth used in professional colour suites, without needing a dedicated monitoring solution or NLE plugin.
Scopes tab - Waveform, Vectorscope, Histogram, CIE xy Chromaticity, and Saturation Response. All five scopes derive from the same 32³ test signal for mathematical consistency.
Scopes
Five scopes, one tab
Waveform (RGB Parade / Luma / Overlay) - read the output exposure distribution and check for highlight clipping or shadow crushing. Vectorscope with 75% and 100% colour bar targets - read saturation output and hue bias direction. Histogram (RGB / Luma / Log Scale) - distribution across the full tonal range. CIE xy Chromaticity with sRGB gamut boundary - verify whether the LUT outputs colours outside the display gamut. Saturation Response - input chroma vs output chroma, coloured by hue - shows exactly which hues the LUT over- or under-saturates and by how much.
Tab 5 - LUT DNA: The Automatic Fingerprint
The LUT DNA tab is the most distinctive feature of the analyzer, and unique among browser-based LUT tools currently available. It automatically characterises the LUT across six measured dimensions, generates a plain-language description of the look, flags practical warnings about clipping and black-point issues, and provides application tips derived directly from the measured data - not from the filename.
LUT DNA tab - radar chart, six key metrics with colour coding, a Channel × Zone breakdown table, auto-generated tags, and a plain-language LUT character description.
LUT DNA
What the six axes measure
Strength - overall magnitude of the colour transformation. Contrast - steepness of the luminance response curve. Saturation - net change to chroma across the full gamut. Warmth - R–B channel divergence indicating colour temperature direction. Green Push - net deviation of the green channel from neutral (significant in film-emulation and teal–orange grades). Smoothness - regularity and predictability of the transformation; a higher score means the LUT is safer to use across varied footage without needing per-clip adjustments.
Auto-generated tags such as Warm, Lifted Shadows, Film Emulation, High Contrast, and Desaturated are derived entirely from measured data. The LUT Character summary is designed to be copied directly into metadata files, project notes, or client delivery documents. The Application Tips section provides dynamically generated guidance based on the specific DNA values - including suggested opacity ranges for strong LUTs and colour space recommendations.
Tab 6 - Compare: Find the Right LUT from a Pack
The Compare tab lets you load a second .cube file alongside the first and perform a side-by-side or overlay comparison of their tone curves. This is the fastest way to narrow down a large LUT pack: load two at a time, compare the Similarity Score and Difference Curve, then eliminate the weaker candidate and load the next contender.
Compare
Reading the metrics
A Similarity Score above 90% means the two LUTs produce the same look at different strength - consider applying one at reduced opacity over the other in your NLE for a blended result. 70-90% = distinct variations from a shared base grade, useful when you want controlled variation across an episode series. Below 70% = fundamentally different approaches - choose based on footage type and creative intent. The Difference Curve shows where the two LUTs diverge most: a peak in the shadows means different black-point treatment; a peak in the highlights means different roll-off behaviour.
Who Is This Tool For?
Colorists & DITs
- Verify LUT behaviour before applying to camera-original footage
- Document LUT DNA for client deliveries
- Detect gamut violations before final render
- Compare creative LUTs against a technical reference transform
Video Editors
- Choose the right LUT from a large pack without trial and error
- Understand why a LUT looks wrong on specific footage
- Verify colour space compatibility before applying
- Export scope screenshots for client review
YouTubers & Creators
- Preview a LUT on a real thumbnail or b-roll frame before committing
- Identify which LUTs in a free pack are strong vs subtle
- Check whether a LUT will crush shadows on your camera
- Build visual consistency across a video series using matching DNA profiles
Photographers
- Evaluate LUT packs in a neutral viewer before batch-processing
- See the actual saturation and contrast impact before processing thousands of images
- Upload a JPEG export and preview the LUT on your own photo before committing
- Identify LUTs with gamut violations that will cause colour shifts in print output
LUT Designers
- Verify that an exported .cube file matches the intended grade
- Compare version iterations to catch regression between builds
- Generate DNA reports for product page documentation and store listings
- Identify unintended gamut clipping before public release
A Practical 60-Second Evaluation Workflow
Here is the fastest practical workflow for evaluating an unknown LUT from a pack, from load to decision:
- Load the .cube file - drag and drop onto the analyzer. (~2 seconds)
- Check LUT DNA - read the Strength metric and the auto-generated tags. A Strength value above 35 indicates a strong LUT; plan to apply at reduced opacity in your NLE. Tags like “Log Input” or “Technical” warn that the LUT is not designed for display-referred footage. (~5 seconds)
- Check Warnings - if highlight clipping or shadow-crushing warnings are present, you will need to protect the extremes before applying. (~5 seconds)
- Read the Curves - note the S-curve shape (contrast level), channel divergence (colour temperature direction), and the shadow toe (black point behaviour). (~10 seconds)
- Preview on your image - upload a representative frame, drag the split divider across skin tones and neutral greys, and decide whether this look suits your footage. (~20 seconds)
- Compare if still unsure - load the closest competing LUT into the Compare tab and check the Similarity Score and Difference Curve. (~18 seconds)
Colour space caveat: All analysis in the Scopes and Curves tabs assumes sRGB / Rec.709 display-referred input. If you are working with log-encoded footage (S-Log2, S-Log3, Log-C, BRAW), apply a colour space transform node before the creative LUT in your NLE - then evaluate the combined output. Applying a display-referred LUT directly to log footage produces incorrect results both on screen and in the analyzer.
Try the LUT Cube Analyzer - Free
No account. No installation. Works in any modern browser.
Supports .cube files from 17³ to 65³ - DaVinci Resolve, Vegas Pro, Premiere Pro, FCP, and
more.