Heat Shield Coating
Canon has reached a new level in its efforts to deal with heat buildup in its traditional white-barrel lenses. Canon coated some lenses' barrels in white, which reflects heat, instead of the more common black. This was done to make sure that its lenses would still work perfectly in hot, direct sunlight. The FD600mm f/4.5 S.S.C and FD800mm f/5.6 S.S.C. were the first white-barrel lenses. They were large-aperture telephoto lenses for single-lens reflex (SLR) cameras that came out in 1976. Canon's own research into heat shield coatings began as a way to make lenses more reliable when they were exposed to high temperatures. Through trial-and-error research into the choice and composition ratio of coatings, Canon found ways to make things reflect more infrared light and came up with new ways to keep the temperature of both the coating film and the things it covers from rising. The result is a group of white-barrel lenses that work better when shooting outside in the sun.
Infrared-reflecting pigments are used in our heat shield coating to make it better at reflecting the "heat" part of sunlight. Canon lenses used to come with either a carbon black or a white titanium oxide coating on the outside. On the other hand, carbon black strongly absorbs infrared waves, which cancels out some of the heat shield coating's benefits for reflectivity. Our new heat shield coating is more reflective because it replaces carbon black with a pigment that reflects infrared light. The coating also has titanium oxide and silica on top of it, which makes it more resistant to UV damage. Damage from scratches or abrasion is very hard to do to it. Canon's signature "white-barrel" colour is still present in lenses with the new coating. The Canon heat shield coating was first used on the EF400mm f/2.8L IS III USM and the EF600mm f/4L IS III USM. It started a new era for white-barrel lenses and is now used on all RF lenses with a white body.