Canon's interchangeable lenses, which are mainly used for digital SLR (single-lens reflex) cameras, incorporate Canon's advanced proprietary technologies and know-how. This page introduces some of the technologies employed in Canon's interchangeable lens lineup.
Canon started working on the development of artificial crystallization technology early on and succeeded in creating a fluorite camera lens in 1969. Characteristics of fluorite lenses include (1) an extremely low refractive index, (2) low dispersion and anomalous partial dispersion, and (3) excellent transmittance of infrared and ultraviolet light compared with optical glass. Fluorite lenses also virtually eliminate chromatic aberration.
Effectiveness of Different Materials at Correcting Chromatic Aberration
Ground aspherical lenses help to reduce aberration, the nemesis of image quality. Although such lenses were once just a dream due to difficulties associated with their fabrication and shape, Canon successfully marketed the world's first aspherical lens in the early 1970s, realizing lenses with finely honed descriptive performance.
How an Aspherical Lens Works
UD lens elements enable an even greater number of lenses to correct for chromatic aberration. Two lenses made of UD glass offer almost the same performance as one fluorite lens. In addition, Canon has developed Super UD lenses, which offer dramatically improved optical performance. This has contributed greatly to correcting chromatic aberration while making lenses more compact.
To correct chromatic aberration, Canon developed the BR optics, which has anomalous dispersion characteristics equivalent to those of fluorite. Canon took a hard look at its lens material, starting with the design of its molecular structure, and successfully developed a new organic material for use in its lenses.
The BR optics is capable of greatly refracting blue light (light in the short wavelength spectrum). This makes it possible to achieve excellent rendering performance with large-aperture lenses, for which correcting chromatic aberration was difficult when using conventional technologies, even when shooting at maximum aperture.
Diffraction is a characteristic of light that refers to how it bends around obstacles upon passing by their edges. DO lenses utilize this phenomenon to control the path of light and consist of a spherical glass lens and a special resin diffraction grating. To manufacture DO lenses, delicate, high-precision technologies are required. There are three types of DO lenses: dual-layered, three-layered, and gapless dual-layered lenses.
DO Lens Structure (Overview)
Using a DO lens has made it possible to greatly reduce the size and weight of the 400 mm f/4, which previously was designed using conventional technologies.
Chromatic aberration is reduced by utilizing the reverse chromatic aberration caused by diffraction and refraction.
For SWC, which uses an array of nanostructures arranged on the lens surface, the refractive index is continuously changed to achieve superior glare prevention even if the incoming light has a large angle of incidence.
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When a shake of the hand causes image blur, it is due to the camera itself moving while its shutter is open. The main types of camera shake are angle camera shake (Fig. 1) and shift camera shake (Fig. 2). Angle camera shake can be corrected by the IS, the conventional mechanism for compensating for camera shake. However, shift camera shake (Fig. 2) also has a major effect when taking close-up shots, such as during macro photography.
Canon's Hybrid IS makes it possible to simultaneously correct for angle camera shake and shift camera shake. In addition to the vibration gyro (an angular velocity sensor) used to detect angle camera shake, Hybrid IS incorporates an acceleration sensor to detect shaking in the horizontal and vertical directions. An algorithm is then used to calculate the amount of shake based on the camera movement detected three-dimensionally by these two sensors, which makes it possible to achieve optimal hand-shake correction during macro photography.
Hybrid IS Corrects for Both Angle Camera Shake and Shift Camera Shake
The ratio between the amount of angle camera shake and amount of shift camera shake varies with shooting conditions. As magnification approaches 100% (1X), both the angle camera shake and shift camera shake increase sharply, making correction that much more important.
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Canon achieved its lens-internal motor drive system, which supports its high-precision AF system, by incorporating motors optimized for the specific AF characteristics of various lenses, including everything from fisheye to super telephoto lenses.
Canon's Ultrasonic Motor (USM) converts ultrasonic vibrations to drive lenses in a specific direction.
This USM offers high torque, high responsiveness and the ability to focus quickly. It is ideal for large-aperture lenses and super telephoto lenses.
「EF24-70mm f/2.8L II USM」
This USM achieves high performance in terms of both high-speed, high-precision AF for still images and smooth AF for videos.
「EF70-300mm f/4-5.6 IS II USM」
Canon's Stepping Motor (STM) uses pulse power to drive lenses.
This type of motor offers high responsiveness and control when starting or stopping operation. Due to its simple mechanical structure, it achieves smooth operation.
「EF-S18-135mm f/3.5-5.6 IS USM」
This motor helps achieve a more compact lens size. It is mainly used in such lenses as the EF 40 mm f/2.8 STM "pancake" lens.
「EF40mm f/2.8 STM」