Colour grading

Cameras that record in a log profile (DJI D-Log M, GoPro Flat and similar) look flat and grey until a conversion LUT turns them into normal Rec.709 video. In plain Gyroflow that means rendering twice: once to stabilize, once more in an editor to grade.

FPVFlow applies the LUT during stabilization, in the Color panel, so the exported file is already graded. On top of the LUT there are 13 colour adjustments, which also work without any LUT loaded.

  1. Where the Color panel is
  2. Load a LUT
    1. Supported files
    2. When a LUT does not load
  3. Build a LUT library
  4. Set the LUT intensity
  5. Colour adjustments
    1. Light
    2. Color
    3. Effect
  6. Order of operations
  7. Bit depth and quality
  8. Rec.709 tagging
  9. Export speed and precise colour conversion
  10. Saved with the project and the queue

Where the Color panel is

The Color panel sits in the right-hand column, between Stabilization and Export settings. It is greyed out until a video is loaded.

Everything you set here shows up live in the preview and is applied to the export.

Load a LUT

  1. Load your video as usual.
  2. In the Color panel, click Load LUT.
  3. Pick a .cube file.

The panel then shows the LUT title (when the file has one) and its size, for example DJI D-Log M to Rec.709 - 33³ entries, with the file path underneath. The button changes to Replace LUT, which swaps the table for another one.

To go back to the original image, click Remove LUT.

A LUT is built for one specific input. A D-Log M to Rec.709 LUT only gives correct colours on footage recorded in D-Log M. The .cube format does not say what input it expects, so FPVFlow cannot check this for you: use the LUT your camera maker publishes for the profile you recorded in.

Supported files

  • Format: Adobe Cube (.cube or .CUBE), the format camera makers ship their conversion LUTs in.
  • Size: 3D tables up to 256 entries per side. The usual sizes are 17, 33 and 65. Tables larger than 65 are downsampled to 65 for processing.
  • Domain: DOMAIN_MIN and DOMAIN_MAX are respected.
  • Interpolation: trilinear, computed in floating point.

The parser also reads 1D tables (LUT_1D_SIZE), but the GPU path, which the preview and exports normally use, only applies 3D tables. Use a 3D LUT. In the same way, Nitidez (sharpness) only applies on the GPU path; the CPU fallback skips it.

When a LUT does not load

If a file cannot be read, the panel shows the reason in red. The message names the problem and, where it applies, the line number:

  • “Expected … entries, found … - the file looks truncated”: the download was cut short. Download the LUT again.
  • “Line … is not three numbers”: a data line is damaged.
  • “No LUT_1D_SIZE or LUT_3D_SIZE in the file”: the file is not a valid .cube LUT.

Build a LUT library

If you use the same few LUTs all the time, point FPVFlow at the folder that holds them once, instead of browsing for a file on every clip.

  1. Click Set LUT folder and choose the folder with your .cube files.
  2. A Library dropdown appears above the buttons, listing every .cube file in that folder, sorted by name.
  3. Pick a LUT from the dropdown to apply it. Choose a LUT… at the top of the list is only a placeholder.

The folder is remembered between sessions and is the same for every project. To use another folder, click Change LUT folder. The dropdown only shows up when the folder contains at least one .cube file.

Set the LUT intensity

Once a LUT is loaded, the Intensity slider blends the graded image with the original, from 0 % (LUT off) to 100 % (full LUT, the default). Lower it when a conversion LUT feels too contrasty or too saturated for your taste.

Moving the slider updates the preview immediately.

Colour adjustments

The adjustments live in the collapsible Basic correction section at the bottom of the panel. It is closed by default, since the common case is a LUT and nothing else. Click it to open it.

The labels follow the app language. The tables below give the English label and, for the Portuguese interface (pt_BR), the label you see there.

All sliders start at 0, which leaves the image untouched. Reset adjustments puts every slider back to 0. The adjustments work with or without a LUT: exposure, contrast and vignette are useful on their own.

Light

All range from -100 to +100 %.

Label In pt_BR What it does
Exposure Exposição Brightens or darkens like opening or closing the aperture, computed in linear light. The ends of the slider are 2 stops either way.
Luminance Luminância A plain brightness gain on the displayed image, up to 50 % either way. Same direction as exposure but a different curve, which is why both exist.
Contrast Contraste Spreads or squeezes the tones around middle grey, so the overall brightness stays put. At -100 the image goes flat grey.
Highlights Destaques Brightens or darkens the upper half of the tonal range.
Shadows Sombras Brightens or darkens the lower half of the tonal range.
Whites Brancos Like highlights, but only the brightest quarter of the tones.
Blacks Pretos Like shadows, but only the darkest quarter of the tones.

The four tonal controls blend smoothly into each other, so there are no hard edges in skies and gradients.

Color

All range from -100 to +100 %.

Label In pt_BR What it does
Temperature Temperatura Positive warms the image (more red, less blue), negative cools it.
Tint Matiz Positive pushes towards magenta, negative towards green. Useful for correcting a green cast.
Saturation Saturação Makes every colour stronger or weaker. At -100 the image is black and white.
Vibrance Vivacidade Saturation that holds back on colours that are already strong, so skies and skin do not blow out first.

Effect

Both range from 0 to 100 %.

Label In pt_BR What it does
Sharpness Nitidez Sharpens the image.
Vignette Vinheta Darkens the corners. Higher values darken more; the centre of the frame is never touched, and the vignette stays round on wide frames.

Order of operations

Colour operations give different results in a different order, so FPVFlow always applies them in the same fixed sequence, after the frame has been stabilized:

  1. Sharpness
  2. Conversion LUT, blended by Intensity
  3. Exposure, luminance, contrast
  4. Blacks, shadows, highlights, whites
  5. Temperature, tint
  6. Saturation, vibrance
  7. Vignette

Note that this is not exactly the order of the sliders in the panel: blacks and shadows act before highlights and whites. Since the adjustments come after the LUT, they work on the converted Rec.709 image, which is what you see in the preview. Sharpening is the exception: it acts on the stabilized source, before the LUT.

Overlays drawn by the app on the preview, such as the safe area, are not graded.

Bit depth and quality

Grading never lowers the quality of the footage:

  • The grading math runs in floating point and is stored in a 16-bit RGB intermediate, so no precision is lost before the final conversion to the bit depth you export in.
  • 10-bit footage stays 10-bit, and log footage converted to Rec.709 keeps smooth skies instead of showing banding.

To actually keep 10 bits, export with a codec and pixel format that support them, in Export settings.

Rec.709 tagging

When a LUT is loaded, the exported file is tagged as Rec.709. Players and editors then show the converted file correctly, instead of treating it as log footage.

Without a LUT, the file keeps the colour tags of the source, even if you used the adjustments: adjustments alone do not turn log into Rec.709, so tagging the file as Rec.709 would be wrong.

Export speed and precise colour conversion

To apply a LUT or any adjustment, every frame has to be converted to RGB and back, on the CPU. By default this conversion uses a fast filter and every CPU core. On 4K footage with a LUT, this took exports from about 7 fps to about 30 fps on a Mac with an M4 Pro.

The Precise color conversion (slower export) checkbox, in the Color panel, makes the conversion use the Interpolation method chosen in Export settings instead. The frame is not resized at this step, only the colour channels are resampled, so the visible difference is small and the cost in render speed is large.

Leave Precise color conversion (slower export) off unless you see a problem in fine coloured detail. Clips with no LUT and every adjustment at 0 skip the conversion entirely, so the option makes no difference for them.

The checkbox is remembered between sessions and saved with each project and render queue job.

Saved with the project and the queue

The LUT, its intensity, the adjustments you changed and the precise conversion option are saved in the .gyroflow project file, and kept per clip in the render queue. Reopening a project or the app restores each clip’s grade.

The project stores the location of the .cube file, not a copy of it. If you move or rename the LUT, load it again.