The measured and perceived brightness of an image also depends heavily on the surface upon which it is projected. Projection display screens are often a reflective white color that may even have some gain built in to redirect more of the light towards the viewer to make the image appear brighter. Most surfaces not engineered for displays (for example, concrete) will be lambertian whic means any light reflected off the surface will be scattered equally in all directions so the apparent brightness of the surface appears the same from all angles. The color, texture, and material itself can greatly affect the perceived brightness of the DGP image. The brightness of the image on different surfaces can be determined by the material reflectivity, along with the projector flux and image size. The reflectivity for several typical ground surfaces can be found in the table below, but these may change significantly based on specific composition along with many other environmental factors.

The conversion between illuminance (lux) to luminance (cd/m²) is relatively simple for a lambertian surface. Most pavement and ground surfaces are assumed to be lambertian.