alba optics delta aflens photocromaticDELTA uses VZUM AF LENS, a photochromatic lens that adapts itself to the intensity of the light present in the environment and automatically changes colour, shielding off harmful UV rays of any sort. Their temporary transformation takes place in a short period of time but it is, nevertheless, gradual and independent of any atmospheric factors. The optical strain is therefore reduced to a minimum and the lenses remain active even on a cloudy day.