Edge Blend Calculator
Plan a multi-projector edge-blended image. Work out the blended canvas resolution, overlap in pixels and metres, total image size, per-projector throw and the exact blend zone for every projector, or work backwards from a target canvas to the overlap you need.
Projectors & Overlap
Physical Image Size
Pick what you already know. Square pixels and a rectangular, keystone-free image are assumed.
Throw ratio is distance ÷ the projector's native image width, so in portrait it applies to the image height on the wall. Check lens options in the Projection Throw Calculator.
Blended Canvas
Canvas width = n × w − (n − 1) × overlap, and the same for height with the number of rows. Need a different shape? Compare it in the Aspect Ratio Calculator.
Raster Layout
Each projector's raster drawn to scale on the blended canvas. Shaded bands are blend zones; where two zones cross (grids), four projectors overlap.
Blend Zones
Pixel ranges on the blended canvas, counted from 0 and inclusive. In each projector's own raster the left blend is always pixels —.
| Column | Canvas X range | Left blend | Right blend |
|---|
| Row | Canvas Y range | Top blend | Bottom blend |
|---|
Reverse: Target Canvas → Overlap Needed
Uses the projectors, orientation and vertical overlap above. Enter the canvas width you need in pixels, or the aspect ratio the blended image must have.
Blending Guidance
- How much overlap? There is no standard. Blending-software makers recommend roughly 10–25 % of the projector's width: VIOSO advises at least 10 % and avoiding more than 25 %, because larger overlaps waste pixels and brightness, and Resolume recommends a minimum of 15 %. Wider overlaps hide small brightness and colour differences between projectors better. Check your projector's or media server's blending documentation.
- Brightness doubles in the overlap before blending. Two projectors light the same area, so the blend ramps must fade each one out so the sum matches the single-projector areas. Ramps are set with the projector or media server's gamma in mind, otherwise a light or dark band shows.
- Black level rises too. No projector outputs true black, and blending can only dim the video signal, so the overlap shows the black level of both projectors (four at the crossing point of a grid). On dark content a grey band appears. Fix it with black-level compensation (lifting black outside the overlap to match), or optically with blend plates or blinders in front of the lenses.
- Use whole pixels and the same overlap on every seam. Media servers and projector blend menus set blend width in pixels, so round the overlap and keep it identical across seams. Match the projector models, lenses, colour settings and light-source hours as closely as possible.
- Lens shift beats keystone. Digital keystone or warping resamples the image and moves pixels, so the figures here (which assume a rectangular raster) become approximate once warping is applied.
Notes & References
- Canvas size: W = n·w − (n−1)·o; H = m·h − (m−1)·ov. Percentage overlaps are rounded to whole pixels.
- Resolutions: WUXGA 1920×1200 (VESA), 1080p 1920×1080 and UHD 3840×2160 (ITU-R BT.709 / BT.2020 image formats), DCI 4K 4096×2160 (DCI Digital Cinema System Specification container).
- Overlap guidance: VIOSO, Preparation – Projector (helpdesk.vioso.com), and Resolume, Edge Blending (resolume.com). Optical blend accessories: Christie Edge Blending Kit product information.
- Physical size assumes square pixels, no keystone or warping, and that throw ratio is quoted against the projector's native image width, as projector manufacturers specify it.
- This is a planning aid. Confirm final values with the projector and media-server manufacturer's tools and on site.