BR Lenses
Canon has suppressed the chromatic aberration that was usually found when using conventional lenses by developing fluorite and UD lenses. Especially when it came to wide-aperture lenses with low F values, previous technology was unable to remove chromatic aberration while also reducing size and weight. Light's dispersion properties are the source of chromatic aberration. A lens's focal plane is where all of the light should ideally converge to form a single point. Regrettably, dispersion is an inevitable result of variations in wavelengths' refractive indices. The true reason behind colour bleeding, or chromatic aberration, is this. It is particularly challenging to correct wavelengths in the blue range of the spectrum, which cannot be fully resolved by simply combining concave and convex lenses. This inevitably results in some colour aberration.
Canon created the "BR Lens" in order to address the issue. This composite lens consists of concave and convex glass lenses layered with BR (Blue Spectrum Refractive Optics) optical elements that have anomalous dispersion characteristics that significantly refract blue (short wavelength range) light. Since the BR lens element can be added to other lens elements in ways that may result in significant chromatic aberration, BR lenses offer more design freedom because the blue wavelengths can be substantially corrected. Canon is introducing lenses that can offer distinctive optical characteristics, while also improving performance and decreasing size, by developing new types of lens materials in this way.