Perhaps the most unappreciated major advance in photography in the past decade has been the rapid improvement of coatings on lenses. Not only do coatings help eliminate reflections, ghosting and other aberrations, but they vastly increase the transmission rate (T value) of light through lens elements. This last bit is perhaps the most important because it means that a 24-element lens can wind up being a stop brighter at the sensor end versus a lens without coatings. That’s the difference in image quality – in a light-limited scenario – to the difference between crop and full frame or a couple generations’ improvement of a camera’s sensor technology. In fact, this increased transmission per lens element is in good part why manufactures like Sigma and Canon have felt free to design the more “bonkers” lenses that contain so much corrective glass.
Canon relentlessly pursues coatings improvements, frequently patenting research on application methods (vacuum deposition was all the rage, but now “sputtering” particles is capturing their fancy) and research on refraction properties of different compounds. Last Tuesday, Canon saw published a patent on the use of ytterbium in coatings so as to be able to create thin coatings without imperfections caused by the sputtering deposition method using older coatings compounds. This is the sort of patent and technology that passes without notice normally, but gets added to a larger and larger pile of tech that collectively provides that “wow factor” for the more recent bonkers lenses.
Canon’s research trend shows the number of patents per year dealing with coatings was below 200 prior to the coatings revolution, when the critical technologies hadn’t yet made it into production lenses, but then exploded by a factor of about 10 for the next decade.