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Black Offset Correction with projector masks

Physical Shutters

A highly practical solution involves physically installing custom shutters (or shaders) in front of the projector lenses. These shutters are designed to obscure the areas within the edge-blend region where projector images overlap.

The optimal shape of the physical shutter may vary depending on the projector's image chip. Most DLP projectors, for instance, utilize a "Diamond" Pixel chip (for more information, refer to: https://www.kguttag.com/2012/02/09/ti-dlp-diamond-pixel/).

Construction and Installation of Temporary Shutters:

  1. With the projectors powered on, display a dark scene or a pure black image on your PC.

  2. Obtain a piece of thick paper or thin cardboard. Cut a zigzag pattern along one edge, leaving the opposite end straight. Create a separate piece for each overlapped side of the projector image.

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    Depending on the shape of the overlap region, it may be necessary to slightly curve the zigzag edge and adjust the shutter's distance from the lens. Experiment with the position and shape of the shutter to achieve the best result.

  3. Hold the paper or cardboard in front of the projector lens, testing both the zigzag and straight edges. Select the side that yields the most favorable outcome.

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  4. Repeat this procedure for all edge-blend sides of each projector.

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Upon successful implementation, there should be no perceptible brighter black offset in the overlapped regions. However, this method might introduce areas that appear slightly brighter or darker when projecting bright scenes or images.

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Fortunately, the software includes a blending curve editor that allows for fine-tuning of the blending in the overlapping regions. Adjusting the slider within this editor can achieve perfectly blended overlap zones.

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It may be necessary to iteratively adjust your physical shutters and alternate between displaying white and dark scenes on your computer to achieve optimal results.

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Permanent Shutters

For a more durable and robust solution, permanent, flexible shutters can be constructed. The design and placement of these shutters depend largely on the type and shape of the projector housing. The most natural placement for a frame supporting these shutters is often on the outer ring of the projector lens. When installing, ensure that the frame and shutters do not impede the lens cooling airflow.

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