Correct LED Panels After Calibration

Fine-tune the geometry and brightness of individual LED panels, seams and pixels on a display output after importing a calibration image. Use this when a calibrated LED wall still shows visible seams, shifted panels or brightness differences between panels.

Before you start

• A display output exists and is routed to your LED wall.
• You have a correction image from your calibration tool. For editing (not just viewing), this must be a 32-bit float PFM. An 8-bit or 16-bit image still corrects the output, but the editing controls are disabled.
• The image's third channel carries LED panel indices. Pixels the mapping does not use are marked with a negative value.

Steps

1. Open the LED Panel Correction window

Open it one of three ways:

• View > Other Windows > LED Panel Correction

• Open LED Panel Correction in a display output's Inspector.

• The warp icon beside a display output in the video routing list.

Opening this window does not switch any warp on. A correction and mesh warping are independent — an output can carry either, both or neither.

2. Select the output and import the correction image

Pick your display output from the Select output dropdown, then click Import Image... and choose your PFM file. The strip shows the decoded resolution, bit depth and number of LED panels found. While the file is being read, a progress indicator appears over the picture and the controls are unavailable — the output keeps its previous correction until the new one is ready.

3. Check the panel layout

Turn on Show panels. Every panel the image describes is outlined and tinted by index. If the layout looks like nonsense, the image's third channel is not carrying panel indices — check your calibration tool's export settings.

4. Correct seams between panels

Set the selection mode to Edge. Click between two panels to select the seam. Drag U offset and V offset to close the visible gap. A seam belongs to one panel only — panel A's seam facing B and B's seam facing A are separate, so correcting one moves only that panel's border pixels. Correct both sides of a gap to close it evenly.

Use Brightness to match the brightness along a seam. 100% is untouched. Where a pixel sits at a panel corner (on two seams), it takes the darker of the two brightness values rather than the product — this prevents dark dots at every corner.

5. Correct whole panels

Set the selection mode to Panel. Click a panel to select it. Drag U offset / V offset to shift the entire panel, or adjust Brightness to trim it. A panel brightness change scales all hand-tuned pixels inside it in proportion. Click Reset Panel to drop a panel's correction, its seams' corrections and any single-pixel corrections inside it.

6. Correct individual pixels (optional)

Set the selection mode to Pixel. Zoom in with Ctrl + Wheel — the picture re-renders at zoomed resolution, so individual pixels become selectable. Click a pixel and drag U / V to move it. A pixel that the mapping does not use (negative panel index) cannot be selected.

7. Reload after recalibrating

When your calibration tool regenerates the PFM file, Backstage picks up the change automatically (about 1.5 seconds after the last write). All your corrections are layered on top of the new image — they are never written into the file. Click Reload to force a re-read immediately, or if the file was missing when the project loaded.

Common Mistakes

• Editing controls are greyed out — The imported image is not a 32-bit float PFM. The strip reads Import a 32-bit float PFM to correct pixels. Re-export your calibration as PFM.

• Show panels looks like nonsense — The image's third channel does not carry valid panel indices. Check that your calibration tool exports the panel map in the blue channel.

• Correcting one side of a seam does not close the gap fully — A seam belongs to one panel. Correct the opposite panel's seam as well to close both sides evenly.

• Pixel corrections vanished after a reload — The regenerated image has a different resolution. Per-pixel corrections are tied to pixel indices and are dropped on a resolution change. Panel and seam corrections are kept.

• Cannot select a pixel — The pixel has a negative panel index, meaning the mapping does not use it. These pixels can never be selected or moved.

Tips

• Start with seams, then panels, then pixels. Seam corrections are where most visible artefacts sit, and they survive recalibration at any resolution.

• A whole drag is one undo step. Drag until the correction looks right, then release — you can undo the entire adjustment in one step.

• Brightness above 100% is allowed. If most panels are too bright, trim them down and leave the dim one at 100% rather than pushing it above its calibrated value.

• Use Clear Corrections to start over without re-importing. It drops every correction but keeps the imported image.

• LED panel correction composes with mesh warping. If your LED wall is also curved, warp it with the mesh editor — the correction sits underneath and the two are independent.

Related

Output Warping — full control reference for the LED Panel Correction and Output Warping windows.

Configure Projector Warping (Mesh Warp) — warping a projector output onto a surface.

Route Projectors and Displays to Outputs (Video Routing) — routing displays and projectors to GPU outputs.