Guide · 2 min read · updated 2026-10-05
Edge Blending and Multi-Projector Setups
How to combine several projectors into one seamless image — overlap sizes, blending curves, black-level compensation, stacking, and calculating final resolution.
Large facades, panoramic screens, domes and immersive rooms are rarely covered by one projector. Instead several projectors are combined into one canvas — side by side with edge blending, on top of each other with stacking, or both.
How edge blending works
Two projectors are aimed so their images overlap by a strip — the blend zone. In that strip, each projector fades its brightness from 100% to 0% with a smooth curve. Because the two fades add up, the overlap ends up as bright as the rest of the image and the seam disappears.
The fade must be gamma-corrected: projectors do not respond linearly, so a straight linear ramp produces a visible bright or dark band. All professional mapping tools and media servers offer adjustable blend curves.
How much overlap?
- 10–15% of image width is typical for flat screens and facades with good alignment.
- 15–25% gives more tolerance for alignment drift, uneven surfaces and wide-angle lenses.
- Overlap costs resolution — the pixels in the blend zone are shared.
Use the edge-blending calculator to see the final canvas resolution and coverage for any number of projectors and overlap.
Calculating the final resolution
For n projectors in a row, each w pixels wide, with an overlap of o pixels:
total width = n × w − (n − 1) × o
Three WUXGA projectors (1920 px) with 15% overlap (288 px) give 3 × 1920 − 2 × 288 = 5,184 px.
Black level: the hidden problem
Projectors never produce perfect black. In the overlap, two projectors add their black levels, so in dark scenes the blend zone glows grey. Solutions:
- Black-level compensation: raise the black level everywhere outside the overlap to match it (costs some contrast).
- Laser projectors that switch the light source off on black frames.
- Content design: avoid large pure-black areas spanning seams.
Matching projectors
Use identical models, ideally with similar running hours. Match colour and brightness before blending; differences in white point show up immediately in a seam. Laser projectors stay stable over time much better than lamps.
Stacking for brightness
Stacking aligns two or more projectors on the same area to multiply brightness — common for landmark facades. Each projector is warped so pixels coincide; even a half-pixel error softens the image. Stacking also provides redundancy: if one projector fails, the show continues at reduced brightness.
Automatic calibration
For more than a handful of projectors, camera-based calibration systems project structured-light patterns, observe them with cameras, and compute warps and blends automatically. They save hours on site and allow quick re-alignment if projectors move in the wind or with temperature.
FAQ
Can I blend different projector models?
It is possible but hard: brightness, colour and black level differ. Use identical models whenever you can.
Do I need special software for edge blending?
Most mapping tools — MadMapper, Resolume Arena, TouchDesigner, Millumin, WATCHOUT, PIXERA and disguise — support edge blending. Some projectors also have built-in blending.
How many projectors does an immersive room need?
It depends on room size and resolution goals. A small room may use 6–10 projectors; large immersive venues use dozens to more than a hundred, all blended and synchronised.