News Release

July 2, 2020
Canon Inc.
Canon Optron Inc.

Canon Optron donates artificially crystallized fluorite, recognized for its 50-year legacy of contributing to optical science, to the JCII Camera Museum

TOKYO, July 2, 2020—Canon Inc. announced today that its subsidiary company, Canon Optron Inc. has donated an artificially crystallized fluorite produced at Canon Optron's headquarters in Yuki City, Ibaraki Prefecture, to the Japan Camera Industry Institute (JCII). The crystal will go on display at the JCII Camera Museum in Tokyo's Chiyoda Ward starting tomorrow.

The artificially crystallized fluorite donated by Canon

The artificially crystallized fluorite donated by Canon

Presentation of the artificially crystallized fluorite

Presentation of the artificially crystallized fluorite

The JCII Camera Museum owns and displays a wealth of historically significant photos and photography-related equipment from Japan and many other countries. The museum, in recognition of synthetic fluorite's more 50-year legacy of contribution to photography, has requested that Canon Optron manufacture one of these crystals for display as part of the museum collection.

It has long been known that when combined with optical glass, fluorite, the mineral form of calcium fluoride (CaF2), can correct for chromatic aberration in a manner that is close to ideal. In the more than 50 years since Canon introduced the FL-F300mm f/5.6, the world's first consumer-grade interchangeable lens in May 1969, the company has included lens elements made using synthetic fluorite in many of its high-performance lenses. Canon Optron, in addition to producing synthetic fluorite lens elements for Canon interchangeable-lens camera and broadcast lenses, manufactures lenses for telescopes used by astronomical observatories, ultraviolet microscopes and many other types of optical equipment, helping to advance state of the optics industry.

Comment from Yasunori ICHIKAWA, JCII Camera Museum Steering committee member

"Fluorite possess incredibly unique optical qualities. Because of its high transmission of visible, ultraviolet and infrared light wavelengths, it has long been used in microscopes and various applications of scientific photography. While today, it is used in low-dispersion lens elements, Canon's history of use of fluorite in their high-performance lens designs spans more than 50 years. As an optical material that can be grown in a crystallized form and possesses superb characteristics, the existence of synthetic fluorite is, in my opinion, historically valuable. Starting tomorrow, it will become part of the permanent collection and displayed in the "Lens Corner" of the museum."

About the JCII Camera Museum

Permanent Exhibit "Historical Cameras of Japan", others
Business Hours 10:00 - 17:00
Closed Mondays (Tuesday if Monday is a national holiday),
New Year's holidays and others specified by the Museum
Admission General: 300 yen / Middle school and younger: Free
Group discount for parties of10 or more (General admission: 200 yen)
Address 25 Ichiban-cho, Chiyoda-ku, Tokyo 102-0082 Japan
Website http://www.jcii-camera.or.jp/e/museum/index.html

Reference

To date, Canon has released 37 lens models (including 28 EF lens models) that employ fluorite lens elements, with 10 of those models still produced. (As of July 2, 2020)

FL-F300mm F5.6 Canon’s first interchangeable lens using synthetic fluorite

FL-F300mm F5.6
Canon's first interchangeable lens using synthetic fluorite

EF600mm F4L IS III USM Canon’s latest lens using synthetic fluorite

EF600mm F4L IS III USM
Canon's latest lens using synthetic fluorite

EF lenses that employ fluorite

Product Release date No. of Fluorite elements
FL-F300mm F5.6May 1969*2
FL-F500mm F5.6June 1969*1
FL300mm F2.8 S.S.C. floriteFebruary 1974*1
FD300mm F2.8 S.S.C. floriteOctober 1975*1
FD500mm F4.5LMay 1975*1
New FD300mm F2.8LApril 1981*1
New FD500mm F4.5LDecember 1981*1
New FD100-300mm F5.6 LNovember 1985*1
New FD80-200mm F4LNovember 1985*1
EF100-300mm f/5.6LJune 1987*1
EF300mm f/2.8L USMNovember 1987*1
EF50-200mm f/3.5-4.5LJune 1988*1
EF600mm f/4L USMNovember 1988*1
EF500mm f/4.5L USMMarch 1992*1
EF1200mm f/5.6L USMJuly 1993*2
EF400mm f/2.8L II USMMarch 1996*1
EF100-400mm f/4.5-5.6L IS USMNovember 1998*1
EF300mm f/2.8L IS USMJuly 1999*1
EF500mm f/4L IS USMJuly 1999*1
EF400mm f/2.8L IS USMSeptember 1999*1
EF600mm f/4L IS USMSeptember 1999*1
EF70-200mm f/4L USMSep-991
EF400mm f/4DO IS USMDecember 2001*1
EF70-200mm f/4L IS USMNovember 2006*1
EF200mm f/2L IS USMApr-081
EF800mm f/5.6L IS USMMay-082
EF70-200mm f/2.8L IS II USMMarch 2010*1
EF300mm f/2.8L IS II USMMar-112
EF400mm f/2.8L IS II USMAugust 2011*2
EF500mm f/4L IS II USMMay-122
EF600mm f/4L IS II USMMay 2012*2
EF200-400mm f/4L IS USM EXT1.4XMay-131
EF100-400mm f/4.5-5.6L IS II USMDec-141
EF70-200mm f/4L IS II USMJun-181
EF70-200mm f/2.8L IS III USMSep-181
EF400mm f/2.8L IS III USMDec-182
EF600mm f/4L IS III USMDec-182
  • *Production finished

Characteristics of fluorite

When light meets water or other transparent matter, it is refracted. Lenses are used to take advantage of this property and focus light that passes through them. However, the degree to which light is refracted depends on the color. For example, blue light, which has a short wavelength will be refracted at a steeper angle than red light, which has a long wavelength. For that reason, even light from the same source will be split by color when it passes through a lens and focused on to various different points, leading to the occurrence of color blurring known as "chromatic aberration."

An image captured with a telephoto lens where chromatic aberration can be seen around the edge of the branch in the red square

An image captured with a telephoto lens where chromatic aberration can be seen around the edge of the branch in the yellow circle

Because chromatic aberration occurs in the opposite direction through a convex lens and a concave lens, it is possible to offset the aberration by combining a small-dispersion convex lens with a high-dispersion concave lens to align the direction of light rays with different wavelengths (such as red and blue) together at the same focal point. However, even with lenses that correct chromatic aberration, if you look closely at the focal point, the intermediate green light between the red and blue wavelengths will still converge at a different point. This chromatic aberration, which remains even after chromatic aberration correction design measures are carried out, is called secondary chromatic aberration, or secondary spectrum. The suppression of this secondary spectrum is where fluorite comes into play.

Compared with optical glass, fluorite lenses have a considerably lower refraction index, low dispersion and extraordinary partial dispersion, and high transmission of infrared and ultraviolet light. Achromatic performance can be achieved by making a convex lens with fluorite, rather than optical glass, to decisively reduce secondary spectrum, causing red, blue and green light rays to almost completely converge on the same focal point to significantly reduce the occurrence of chromatic aberration.

Optical characteristics of optical glass and fluorite

Optical characteristics of optical glass and fluorite

The effects of secondary spectrum are more pronounced for telephoto lenses due to their long focal lengths. To that end, Canon employs fluorite in such contemporary lenses as the EF400mm f/2.8L IS III USM and EF600mm f/4L IS III USM (both released in December 2018). This series of telephoto lenses employing fluorite has earned strong support from photographers worldwide for their subtle rendering and high contrast.

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