Fluorite L-Series Lenses
Canon lenses are renowned for their performance and optical quality. And no lenses have a better reputation among professional photographers than Canon's L-series lenses. Identifiable by a distinctive red ring around their outer barrel, these lenses use special optical technologies (Ultra-low Dispersion UD glass, Super Low Dispersion glass, Fluorite elements, and Aspherical elements) to truly push the optical envelope.
L-series telephoto lenses utilize Canon's UD glass to minimize the effect of chromatic aberration, sometimes called colour fringing. UD glass provides outstanding contrast and sharpness in lenses like the 70-200 f/2.8L IS and 300mm f/4.0L IS. Even more effective are fluorite elements. A single fluorite element has the corrective power of two UD glass elements, which gives these L-series lenses their spectacular performance.
Wide-angle lenses and fast normal focal-length lenses often suffer from another optical problem (spherical aberration) which causes an overall softening and optical "smearing" of the image. Canon has developed four different manufacturing technologies to produce Aspherical lens elements, which combat this problem. Aspherical optics, which have an extremely precise variable curvature of one or both sides of a lens element, also allow more compact lens designs and permit lighter lenses with fewer elements. Combined with Canon's exclusive multi-coating technology, Super Spectra Coating, and the attention paid to details such as anti-reflective material inside of lens barrels, L-series lenses virtually eliminate internal ghosting and flare.
In order to achieve critical autofocus, the elements within a camera lens have to move quickly, quietly, and with exacting precision. To accomplish this, Canon developed the world's first lens-based Ultrasonic Motor (USM). Based on a totally new technology, the motor spins by ultrasonic oscillation energy. Therefore, torque is constant and start and stop functions virtually instantaneous.
By making the autofocus operation almost inaudible and by accelerating the autofocus speed, this type of motor greatly expands the shooting possibilities for Canon photographers.
You'll find two types of Canon Ultrasonic Motors in the camera lens system. Ring-type USM-equipped lenses, found in large aperture and super telephoto designs, allow manual focusing without switching out of the auto mode. Micro USM designs bring the performance benefits of Canon's USM technology to a wide assortment of affordable EF lenses.
Optical Image Stabilizer
If all your pictures were taken outdoors on a bright, sunny day you may not find it difficult to capture sharp pictures. But blurred pictures due to camera shake becomes more of a problem when taking pictures in dim light - at dusk, indoors, on a cloudy day. And the chance of getting blurred pictures increases when using longer focal length lenses that magnify the image and any associated movement.
To overcome these problems, Canon developed lenses with built-in image stabilization. The Canon Image Stabilizer uses sensors to detect motion and generate a corrective signal to reduce blur caused by camera movement. An image-stabilizing lens group along the optical axis is shifted in response to the detected motion, providing effective cancellation of unwanted lens movement and vibration. Result � in still photography, high magnification lenses can be hand-held at slower shutter speeds without blurred images, and handheld video footage is smoother.
In many shooting situations where photographers are not allowed to use a tripod or flash, such as art museums and concert halls, Canon lenses with image stabilization are the ticket to sharper pictures.
The development of the DO lens was based on the principle that chromatic aberrations occur in opposite directions in diffractive and refractive optical elements. In other words, it is theoretically possible to eliminate chromatic aberrations in lenses by combining diffractive and refractive optical elements. Since diffractive optical elements have only one diffraction grating, which causes light to branch in unnecessary directions, resulting in such problems as flare, it was unsuitable for use as a camera lens. Canon developed a unique two-layer DO lens by precisely placing two optimized diffractive optical elements a few micrometers apart to create a multi-layer grating. The two-layer DO lens, which Canon incorporated into its EF400mm f/4 DO IS USM interchangeable SLR camera lens, makes possible significant reductions in the size of telephoto lenses, and, at the same time, contributes to greatly improved imaging performance.
Multiple-Zone Evaluative Metering
Canon developed a 21-zone metering sensor to accommodate 45-point area AF. Using a newly developed algorithm, this metering system performs high-speed calculations of output from 21 zone sensors and AF information, and adjusts exposure instantly.
This configuration enables the camera to make compensations appropriate to shooting conditions and maintain exposure stability. The system also incorporates an average metering element that factors in periphery conditions, providing accurate exposure even when the composition changes slightly, or when the subject covers multiple metering points.
EOS Integrated Cleaning System
The EOS Integrated Cleaning System (EOS I.C.S.) incorporated into the EOS DIGITAL REBEL XTi (EOS 400D DIGITAL) is a generic name for Canon's technology for minimizing sensor dust, which is specific to digital SLR cameras. The company focused attention on a series of processes from dust generation to adherence and removal, and came up with a variety of stop measures.
Mechanisms and materials to minimize dust generation
In addition to employing materials and a construction that help prevent the buildup of dust inside the camera, the camera's exterior uses scratch-resistant material in such places as the body cap for the EF mount.
Anti-static technologies to minimize dust adherence
The infrared-cut low-pass filter located right in the front of the CMOS sensor employs an anti-static mechanism to minimize dust from static cling.
Self Cleaning Sensor Unit that removes dust*
The Self Cleaning Sensor Unit consists of the CMOS sensor, which features a sealed structure to keep out dust and the infrared-cut low pass filter; a Sensor Cleaning Mechanism, which uses ultrasonic vibrations to shake off any dust that may accumulate on the surface of the lowpass filter; and peripheral components to adsorb dust shaken off from the filter's surface. Users have the choice of two sensor-cleaning modes: Auto mode, which operates for about one second when power is turned on or off, and Clean Now mode, which is accessible through the menu interface.
Canon Technology Terms
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15 May 2009
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