Shulou(Shulou.com)11/24 Report--

Natural light contains red, green, blue and other different wavelengths of light. Different wavelengths and different refractive indices make it difficult to converge at the same point after refraction through the lens-the resulting image blur is called axial chromatic aberration (also known as longitudinal chromatic aberration). Reflected in the photo, the focus appears purple halo before (near the camera direction) and green halo after the focus (out-of-focus direction).

In previous optical designs, it was difficult to converge short-wavelength blue light with other wavelengths. In order to solve this problem, Canon and Nikon successively introduced "blue high refraction" lenses to greatly reduce the axial color difference and improve the picture clarity of large aperture lenses and telephoto / ultra-telephoto lenses.

Refraction of red, green and blue light by ▲ ordinary optical elements

Refraction of red, green and blue rays by ▲ blue high refractive lenses (Canon BR)

Refraction of ▲ ordinary Convex-concave Lens

The refraction of ▲ after adding blue light high refraction lens (Canon BR) Canon BR lens Canon's "blue light high refraction" lens is called BR lens. It consists of a convex lens, a concave lens and a BR optical element (organic optical material). It was first applied to EF 35mm F1.4L II in August 2015.

Canon uses BR lenses mainly in large aperture fixed focus lenses. As of March 2023, other products using BR lenses include RF85mm F1.2L USM (released in May 2019) and RF85mm F1.2L USM DS (released in October 2019).

Optical structure of ▲ RF85mm F1.2L USM

Nikon SR lenses Nikon's "blue light high refraction" lenses are called SR lenses. Unlike Canon BR, Nikon SR is a single glass lens. According to the previously exposed patent, SR lenses are made of glass mainly composed of phosphorus oxide, which can take into account light transmittance, refractive index, durability and lightweight.

Nikon uses SR lenses widely in the new generation of telephoto lenses. As of March 2023, products that use SR lenses are

AF-S Nikkor 120-300mm F2.8E FL ED SR VR (released January 2020)

Z 70-200mm F2.8 VR S (released January 2020)

Z 400mm f / 4.5 VR S (released June 2022)

Z 400mm f / 2.8TC VR S (released January 2022)

Z 600mm f / 4 TC VR S (released November 2022)

Z 800mm f / 6.3 VR S (released April 2022)

Optical structure of ▲ Z 400mm f / 4.5 VR S other brands HOYA released a new high dispersion lens model FD270 at the end of 2020, with special reference to high refractive index for short wavelength light. Many lens manufacturers will buy HOYA lenses, so we have reason to believe that more manufacturers will introduce lenses with "blue high refraction" technology in the future.

(the picture is translated by machine) this article is from the official account of Wechat: camera Notes (ID:xjbiji), by Teng Fei et

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