RDL peripheral illumination ratios are as follows

Horizontal: 58%
Diagonal: 45%

In the central projection method used by the RDL, the vignetting ratio decreases according to the cosine fourth law. The vignetting ratio is inversely proportional to the distortion factor, and if one is raised, the other is lowered. Therefore, a lens unit with a low distortion rate, such as the RDL, will have a higher peripheral illumination ratio.