A professional videographer has definitively debunked a widespread rumor claiming Sony rear lens caps are 18% grey and can be used for color calibration. In an Instagram Reel, cinematographer Chung Dha Lam demonstrated that the ALC-R1EM lens cap is a much darker shade and "not even in the same ballpark" as a true middle grey card.
Middle grey (18% grey) is a critical reference tone cameras use for accurate auto-exposure and white balance. Using an incorrect reference, like the darker Sony cap, can lead to poorly exposed and color-shifted images. This myth has been propagated recently by several photography influencers and even appeared on Sony's own help forums.
For correct calibration in tricky lighting, photographers should use a proper color chart or grey card, not a lens cap. The origin of the false claim remains unknown, but experts urge photographers to ignore this misleading advice.