Blend Multiple Projectors

Last updated 14 September 2026

When two or more projectors in the same render group cover the same surface, Backstage blends their overlapping edges automatically. This page covers enabling blending, adjusting the blend curve, and verifying the result.

Before you start

  • A scene group with a render group exists, containing at least two projectors aimed at the same surface
  • The projectors physically overlap by roughly 10–20 % of the image width
  • Each projector is geometrically calibrated (warped to the surface)
  • Content is assigned to the surface and playing

Steps

1. Enable blending on the render group

Select the scene group that holds your projectors. In the group’s properties, expand the Blending section and check Enable.

Blending is automatic. Every projector in the render group already covers every surface in that group by default. Where two projectors overlap on the same surface, Backstage computes the blend weights from their warp meshes — there is no manual overlap width to set.

2. Adjust the blend curve with Gamma

In the same Blending section, drag the Gamma value. This shapes the brightness falloff across the overlap zone.

Gamma

Effect

2.2

Good starting point for most projectors

2.5–3.0

Darker transition — try this if the overlap appears brighter than the rest

1.8–2.1

Lighter transition — try this if the overlap appears darker than the rest

3. Optional — enable debanding

If you see visible banding in the blend zone (especially on dark gradients), check Enable debanding in the same Blending section. This adds a small amount of noise to smooth the gradient.

4. Optional — enable brightness correction

Still in the group’s Blending section, expand the Brightness Correction tree. Set Mode to Local or Global. Use Adjustment to control how strongly the correction is applied.

Brightness correction reduces the brightness of the blended area to match the non-overlapping areas. It is optional — content that is continuously bright may not need it.

5. Check the result

Project a uniform white or grey test image across the full surface. A good blend is invisible — no seam, no bright band, smooth brightness across the full width.

Common Mistakes

  • Blending enabled but no visible effect — the projectors are not in the same render group, or they are not aimed at the same surface. Blending is computed per render group.

  • Bright seam at the join — Gamma is too low. Increase it until the overlap matches the surrounding brightness.

  • Dark band at the join — Gamma is too high or brightness correction is over-applied. Lower the Gamma or reduce the Adjustment value.

  • Setting masking before understanding blending — Masking (blend limitation) is for trim-gate rigs, not for defining the blend zone. In a standard setup, blending is automatic once projectors overlap. Editing masking on a normal rig restricts which pixels participate and can make the blend worse.

Tips

  • Start with a Gamma of 2.2 and adjust by eye on a uniform test image. Small changes make a visible difference.

  • The overlap width is set by physical projector positioning. Move the projectors closer together to widen it, further apart to narrow it.

  • For more than two projectors, the same principle applies — every projector in the render group participates in blending wherever it overlaps another.

  • For dark content, consider running a black level correction with CalibratorLite after setting up blending.

Use Camera Calibration (CalibratorLite) — camera-based calibration and black level correction

Create a Display — single-projector setup from scratch

Panoramic Projection - Projection Wizard — panoramic multi-projector rigs