Uneven illumination and hotspots in an LED light box is almost always caused by one of three things.
Poor diffuser quality is the most common cause. The diffuser scatters light evenly between the LEDs and the graphic. A low-quality diffuser does not scatter effectively and visible hotspots appear where the LEDs are densest.
Incorrect LED density is the second cause. Cheap frames cut costs on LED count, meaning the centre of the panel is noticeably dimmer than the edges.
The graphic itself can also be a factor. Very thin or low-opacity print materials transmit rather than diffuse the light which causes the hotspots in an LED light box.
The solutions:
- Specify a back-lit format for large panels rather than edge-lit
- Buy from suppliers who can specify the diffuser quality
- Use print materials with appropriate opacity for the backlit application