Lens Glossary of Terms
APS-C: Advanced Photo System type-C (APS-C) is an image sensor format approximately equivalent in size to the Advanced Photo System "classic" size negatives. These negatives were 25.1 x 16.7 mm and had an aspect ratio 3:2.
Sensors meeting these approximate dimensions are used in many digital single-lens reflex cameras, in addition to a few large-sensored live-preview digital cameras (such as the Sony DSC-R1 and the Sigma DP1) and a few digital rangefinders (e.g. the Epson R-D1). Such sensors exist in many different variants depending on the manufacturer and camera model. All APS-C variants are considerably smaller than 35 mm standard film which measures 36×24 mm. Sensor sizes range from 20.7×13.8 mm to 28.7×19.1 mm. Each variant results in a slightly different field of view (FOV) from lenses at the same focal length and overall a much narrower field of view compared to 35 mm film.(1)
Most DSLR and 3rd party lens manufacturers now make lenses specifically designed for APS-C cameras. The designations by brand include:
Nikon DX format
Tamron Di II
A focal length multiplier (FLM) also known as a "crop factor" can be used to calculate the 35 mm equivalent focal length from the actual focal length. The most common multiplier ratios (in order of announcements):
1.6× — Canon EOS 40D, Canon EOS 400D, Canon EOS 30D, Canon EOS 20Da, Canon EOS 350D, Canon EOS 20D*, Canon EOS 300D*, Canon EOS 10D*, Canon EOS D60*, Canon EOS D30*
1.5× — all Nikon DSLR, all Fuji DSLR (Fuji uses Nikon bodies), Sony DSLR-A100 (with technology from Konica Minolta), Konica Minolta Maxxum 5D*, Konica Minolta Maxxum 7D*, All Pentax DSLR
1.3×↑ — Canon EOS-1D Mark III, Canon EOS-1D Mark II N, Canon EOS-1D Mark II*, Canon EOS-1D*
[Re] Calibration: Also known as 'servicing' a lens. Sending a lens back to the manufacturer to be calibrated due to age, for defects or part replacement.
Chromatic aberration: In optics, chromatic aberration is caused by a lens having a different refractive index for different wavelengths of light (the dispersion of the lens). The term "purple fringing" is commonly used in photography, although not all purple fringing can be attributed to chromatic aberration.
Longitudinal and lateral chromatic aberration of a lens is seen as "fringes" of color around the image, because each color in the optical spectrum cannot be focused at a single common point on the optical axis.
Since the focal length f of a lens is dependent on the refractive index n, different wavelengths of light will be focused on different positions. Chromatic aberration can be both longitudinal, in that different wavelengths are focused at a different distance from the lens; and transverse or lateral, in that different wavelengths are focused at different positions in the focal plane (because the magnification of the lens also varies with wavelength).
Similar colored fringing around highlights may also be caused by lens flare. Colored fringing around highlights or dark regions may be due to the receptors[clarify] for different colors having differing dynamic range or sensitivity -- therefore preserving detail in one or two color channels, while "blowing out" or failing to register, in the other channel or channels. On digital cameras, the interpolation technique is likely to affect the apparent degree of this problem.
On photographs taken using a digital camera, very small highlights may frequently appear to have chromatic aberration where in fact the effect is because the highlight image is too small to stimulate all three color pixels, and so is recorded with an incorrect color. This may not occur with all types of digital camera sensor. Again, interpolation technique may affect the apparent degree of the problem. (1)
Crop Factor: See APS-C: above
Elements (#'s): The complexity of a lens—the number of elements and their degree of asphericity—depends upon the angle of view and the maximum aperture, among other things. An extreme wideangle lens of large aperture must be of very complex construction to correct for optical aberrations, which are worse at the edge of the field and when the edge of a large lens is used for image-forming. A long-focus lens of small aperture can be of very simple construction to attain comparable image quality; a doublet (with two elements) will often suffice. Some older cameras were fitted with "convertible" lenses of normal focal length; the front element could be unscrewed, leaving a lens of twice the focal length and angle of view, and half the aperture. The simpler half-lens was of adequate quality for the narrow angle of view and small relative aperture. Obviously the bellows had to extend to twice the normal length.
Good-quality lenses with maximum aperture no greater than f/2.8 and fixed, normal, focal length need three (triplet) or four elements (the trade name "Tessar" derives from the Greek tessera, meaning "four"). The widest-range zooms often have fifteen or more. The reflection of light at each of the many interfaces between different optical media (air, glass, plastic) seriously degraded the contrast and color saturation of early lenses, zoom lenses in particular, especially where the lens was directly illuminated by a light source. The introduction many years ago of optical coatings, and advances in coating technology over the years, have resulted in major improvements, and modern high-quality zoom lenses give images of quite acceptable contrast. (1)
F (f/stop, F#): In optics, the f-number (sometimes called focal ratio, f-ratio, or relative aperture) of an optical system expresses the diameter of the entrance pupil in terms of the effective focal length of the lens. It is the quantitative measure of lens speed, an important concept in photography. (1)
Fast [lens]: Term used to describe a lens with a low F/Stop. Such lenses allow in more light to strike the sensor which raises the shutter speed (thus, calling them 'fast').
Full Frame (Sensor): Users familiar with conventional 35 mm SLR film cameras generally know how they want to render their subject and have a rough idea of how the picture will look in terms of perspective based on such factors as the focal length of the interchangeable lens used. Image sensors (CCD and CMOS sensors) in most digital SLR cameras, however, are smaller than the size of a single frame of 35 mm film (36 x 24 mm). To correctly estimate how the subject will look, it is necessary to calculate the difference compared to a frame of 35 mm film, based on the focal length of the interchangeable lens used.
In 2002, Canon developed its own full-frame 35 mm CMOS sensor, measuring 36 x 24 mm, and incorporated it into the company's top-of-the line EOS-1Ds digital SLR camera. This development enabled users to utilize the full range of interchangeable lenses for EOS-series SLR cameras, ensuring faithful angles of view and perspectives according to the lens's focal length.
Furthermore, in 2004, Canon developed a second-generation CMOS sensor boasting exceptional image resolution with approximately 16.7 million effective pixels.
Hood [lens]: In photography, a lens hood is a device used on the end of a lens to block the sun or other light source in order to prevent glare and lens flare.(1)
Infrared-Cut Low-Pass Filters: The appearance of false colors — colors not found in the actual subject — and moiré patterns are phenomena specific to digital cameras. They occur when light of high spatial frequency (typically in fine patterns or boundaries between light and dark areas) enters only a single pixel, causing the light to be perceived as a color different from the original color.
The optical low-pass filter, located directly in front of the CMOS sensor, is designed to reduce these problems. Canon developed a new three-layered optical low-pass filter in response to increasing CMOS pixel counts. Two of the three layers are single-crystal substrates that separate the image data into horizontal and vertical directions. To preserve image sharpness while cutting the high-spatial-frequency component of the image that causes false colors and color moirés, a phase plate designed to apply circular polarization to light is sandwiched between these substrates and the image data is accurately separated. Additionally, this optical low-pass filter features a hybrid structure that incorporates an infrared-cut filter to suppress ghosting and color fogging.
IQ (Image Quality): A term used to describe the quality of an image usually by, but not limited to color, contrast, and sharpness.
Normal [lens]: angle of view of the diagonal about 50° and a focal length approximately equal to the diagonal produces this angle.
Macro [lens]: angle of view narrower than 25° and focal length longer than normal. These lenses are used for close-ups, e.g., for images of the same size as the object. They usually feature a flat field as well, which means that the subject plane is exactly parallel with the film plane.
OoF or oof: Net-speak for “Out of Focus”. There are many reasons for images not being in focus; lens shake, focusing on the wrong point and a defective mechanism within the lens are but a few reasons.
Prime [lens]: Fixed focal length lens (i.e. Canon EF 50mm F1.2). Considered to be the 'sharpest' lens type.
Soft: Term used to describe less-than-perfect image clarity. Prime lenses are believed to be the 'sharpest' lenses. Reasons for soft images very widely (see OoF above) and is generally considered a bad image trait. Not to be confused with the post processing 'blur' added to some photos for effect.
Teleconverter: A teleconverter or doubler is a group of lenses which is mounted between the camera and a photographic lens. Its job is to enlarge the central part of an image obtained by the objective lens. For example a 2× teleconverter enlarges the central 12×18 mm part of an image to the size of 24×36 mm. Teleconverters are typically made in 1.4×, 2× and 3× models.
The use of a 2× teleconverter gives the effect of using lens with twice the focal length. It also decreases the amount of light reaching the film by the factor of 4 (an equivalent of doubling the focal ratio) as well as the resolution (by the factor of 2). (1)
Telephoto [lens] or long-focus [lens]: angle of view narrower and focal length longer than normal. A distinction is sometimes made between a long-focus lens and a true telephoto lens: the telephoto lens uses a telephoto group to be physically shorter than its focal length.
Wide-angle [lens]: angle of view wider than 60° and focal length shorter than normal.
Zoom lens: Some lenses, called zoom lenses, have a focal length that varies as internal elements are moved, typically by rotating the barrel or pressing a button which activates an electric motor. Commonly, the lens may zoom from moderate wide-angle, through normal, to moderate telephoto; or from normal to extreme telephoto. The zoom range is limited by manufacturing constraints; the ideal of a lens of large maximum aperture which will zoom from extreme wideangle to extreme telephoto is not attainable. Zoom lenses are widely used for small-format cameras of all types: still and cine cameras with fixed or interchangeable lenses. Bulk and price limit their use for larger film sizes. (1)
Aspherical lenses: Ordinary spherical elements have an inherent flaw in that the point of focus for the lens center does not match that of the lens periphery. Spherical aberrations of large-aperture lenses and distortion by ultra-wide-angle lenses cannot be resolved with spherical elements alone. The Aspherical lens element was therefore developed. The curvature of the lens element is calculated and shaped to achieve the ideal single point of focus. The result is high contrast with minimal flare, even with a large aperture lens. Distortion can also be effectively corrected in ultra -wide-angle lenses. Canon started to develop manufacturing technology for Aspherical elements early on. We eventually succeeded in establishing mass-production grinding and polishing process with a polishing process of 5/10,000mm. In 1971, Canon marketed the FD 55mm f/1.2AL lens, the worlds first large-aperture Aspherical lens for SLRs. This was followed by many other Canon lenses incorporating Aspherical elements and they were well received.
Also, Canon developed mass-production technology for glass-molded Aspherical elements and replicated Aspherical lenses. The former was produced by an ultra-high-precision Aspherical lens-molding machine which shaped the glass directly. For the latter, the Aspherical surface was formed by ultraviolet-hardened resin film applied on a spherical element. Canon has developed numerous compact-size lenses, taking full advantage of Aspherical elements to attain high image quality.
Canon FD (Lens Mount): The Canon FD lens mount is a physical standard for connecting a photographic lens to a single-lens reflex camera body. The standard was developed by Canon of Japan and was introduced in March 1971 with the Canon F-1 camera. It was the primary Canon SLR lens mounting system until 1987 when the cameras from the Canon EOS series were first produced. The last camera in the FD system was the Canon T60, from 1990. The FD mount replaced Canon's earlier FL mount; FD-mount cameras could use FL lenses in stop-down metering mode. There is no known meaning for 'FD', and Canon has never disclosed what, if anything, it stands for.
Although the Canon FD system enjoyed huge popularity in the 1970s and 1980s, the mount system is now obsolete, and Canon FD cameras and lenses are available for low prices on the second-hand market. The makes the system very attractive to 35mm film photographers who demand the highest optical quality, but who do not need autofocus capability. (1)
Canon EF (Lens Mount): The EF lens mount allows all the Canon EF lenses to be used on any of the Canon EOS line of cameras made by Canon Inc. Unlike the EF's breech-lock predecessor, the FD mount, the EF mount uses a bayonet-style mount. EF stands for "Electro-Focus": automatic focusing on EF lenses is handled by a dedicated electric motor built into the lens. All communication between camera and lens takes place through electrical contacts; there are no mechanical levers or plungers.
Canon EF-S (Lens Mount): The EF-S lens mount is a derivative of the EF lens mount created for a subset of Canon digital single-lens reflex cameras with APS-C sized image sensors.
The "S" in EF-S stands for "short back focus", which means that the rear element of the lens is closer to the image sensor than on regular 35 mm SLR cameras. The proximity of the rear element to the image sensor greatly enhances the possibilities for wide angle and very wide angle lens, enabling them to be made smaller, lighter (containing less glass), faster (larger aperture) and less expensive. Most current Canon EF-S lenses are wide angle.
Lenses designed specifically for APS-C sized sensors are often optically designed to provide a narrower light cone to match the sensor. However, not all such lenses require the shorter back focus, and may feature the standard EF mount. Such lenses will give noticeable vignetting if used on a 35mm film or sensor camera. (1)
DO (Diffractive Optics/Optical): The refractive index of light changes slightly according to the wavelength. As light passes through a lens, this difference in refractive index results in chromatic aberrations and reduced image quality. One way to correct chromatic aberrations is to combine convex and concave lenses. In the case of telephoto and zoom lenses, in particular, the large number of lens elements needed to correct chromatic aberrations results in larger lens sizes. Canon developed the world's first Diffractive Optical Element (DO lens) for cameras, solving the problem of chromatic aberration and, at the same time, achieving smaller lens sizes.
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.
The next challenge was to incorporate the DO lens into zoom lenses. In the case of zoom lenses, the angle of light incidence changes considerably in response to changes in focal length, causing flare in two-layer diffractive optical systems. Canon studied the refractive index of diffractive optical elements as well as the shape of multi-layer gratings and came up with a three-layer DO lens that utilizes three diffractive optical elements. Incorporating the three-layer DO lens into the EF70- 300mm f/4.5-5.6 DO IS USM zoom lens, Canon successfully achieved a reduction in the size of telephoto zoom lenses.
EOS (Electro-Optical-System): “The EOS auto-focus 35 mm film and digital SLR camera system was introduced in 1987 with the Canon EOS 650 and is still in production as Canon's current dSLR system. The acronym EOS was chosen for Eos, the Titan Goddess of dawn in Greek mythology, and is often pronounced as a word, although some spell out the letters. There is no officially correct way, as both ways mean something logical.” (1)
EOS Integrated Cleaning System: The EOS Integrated Cleaning System (EOS I.C.S.) incorporated into the EOS DIGITAL REBEL XTi (EOS 400D DIGITAL) and EOS 40D 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.
IS (Image Stabilization): No matter how great the lens is, camera shake can spoil the shot. Blurred photos due to camera shake usually occur when the shutter speed is slower than the reciprocal of the lens focal length. For example, a shutter speed slower that 1/200 sec. at the 200mm focal length can invite a blurred photo caused by camera shake. In such cases, a tripod is necessary. However, a tripod can be heavy and troublesome burden when you go hiking or traveling. There are even places where using tripods is prohibited. Using a slow shutter speed then becomes difficult. To resolve this problem, Canon became the first manufacturer to incorporate an Image Stabilizer in an SLR camera lens. Optical shake is detected by gyro sensors, which provide the data necessary to shift the image-stabilizing lens group in parallel to neutralize the shake. This increases the usable shutter speed range by up to 2 full steps for hand-held shooting. Except for the EF28-135mm f/3.5-5.6 IS USM and EF 75-300mm f/4-5.6 IS USM lenses, IS lenses have two IS modes. One is for normal image stabilization and the other is for panned shots. With a monopod, the Image Stabilizer on all IS lenses operates normally as during hand-held shooting. Also, the EF 300mm f/2.8L IS USM, EF 400mm f/2.8L IS USM, EF 500mm f/4L IS USM, and EF 600mm f/4L IS USM lenses have a mechanism that allows the Image Stabilizer to function properly while the lens is mounted on a tripod.
L (Luxury Class Lens): L Class lenses are of a more rugged design, have superior optics, feature a red ring and are typically white. More recent L Class lenses feature a weather resistant design to help protect lens internals from moisture and dust.
UD (Ultra low Dispersion): The refraction of light differs depending on the wavelength. The point of focus therefore differs depending on the different wavelengths or colors. When the different wavelengths are focused at different points, the colors look smeared. This is called chromatic aberration. The longer the focal length, the more pronounced chromatic aberration becomes. Usually, an achromatic element is used in a lens to correct chromatic aberration. However, normal optical glass can only be corrected for two primary spectral colors. An exception to this limitation is Fluorite, an ideal material. Fluorite, which is crystalline, has abnormally low refraction and dispersion characteristics, which optical glass cannot achieve. It also has anomalous dispersion from the green to blue wavelengths. Canon developed production technologies to manufacture fluorite. By incorporating Fluorite in lenses, the points of focus of the three primary spectral colors of red, green and blue all meet at one point for ideal correction of chromatic aberration. There is also UD-glass, which is a special type of optical glass whose properties nearly match those of Fluorite. The effect of two UD-glass elements gives almost the same effect as one Fluorite element. And one super-UD-glass element gives almost the same effect as one Fluorite element.
EF 24mm f/1.4L USM
EF 135mm f/2L USM
EF 200mm f/2.8L II USM
EF 300mm f/2.8L IS USM
EF 300mm f/4L IS USM
EF 400mm f/2.8L IS USM
EF 400mm f/4 DO IS USM
EF 400mm f/5.6L USM
EF 500mm f/4L IS USM
EF 600mm f/4L IS USM
EF 1200mm f/5.6L USM
TS-E 24mm f/3.5L
EF 180mm f/3.5L Macro USM
EF 16-35mm f/2.8L USM
EF 24-70mm f/2.8L USM
EF 28-300mm f/3.5-5.6L IS USM
EF 70-200mm f/2.8L USM
EF 70-200mm f/2.8L IS USM
EF 70-200mm f/4L USM
EF 70-200mm f/4L IS USM
EF 100-400mm f/4.5-5.6L IS USM
Tilt-Shift Lenses: With a Canon TS-E lens, you can control the angle of the plane of focus and the picture's perspective. The effects of large-format camera movements can be obtained with the TS-E lenses for EOS cameras. Although manual focusing is required, automatic aperture control enables auto exposure and auto exposure bracketing. The tilt and Shift axes normally intersect at a 90 degree angle, but can be made parallel to each other.
TS-E lenses are capable of tilt and shift movements that greatly expand picture-taking possibilities. Tilt movements alter the angle of the plane of focus between the lens and film plane, and shift movements move the lens optical axis in parallel.
TS-E 90mm f/2.8
TS-E 24mm f/3.5L
TS-E 45mm f/2.8
USM (Ultrasonic Motor): An ultrasonic motor is a type of electric motor formed from the ultrasonic vibration of a component, the stator, placed against another, the rotor or slider depending on the scheme of operation (rotation or linear translation). Ultrasonic motors differ from piezoelectric actuators in several ways, though both typically use some form of piezoelectric material, most often lead zirconate titanate and occasionally lithium niobate or other single-crystal materials. The most obvious difference is the use of resonance to amplify the vibration of the stator in contact with the rotor in ultrasonic motors. Ultrasonic motors also offer arbitrarily large rotation or sliding distances, while piezoelectric actuators are limited by the static strain that may be induced in the piezoelectric element. (1)
Nikon - SWM, Silent Wave Motor
Minolta, Sony - SSM, SuperSonic Motor
Pentax - SDM, Sonic Direct-drive Motor
Sigma HSM, HyperSonic Motor
Olympus SWD, Supersonic Wave Drive
Weather Resistant (Models): The EF300mm f/2.8L USM, EF 400mm f/2.8L IS USM, EF 500mm f/4L IS USM, and EF 600mm f/4L IS USM lenses are highly dust- and water- resistant. The switch panel, exterior seams, and drop-in filter compartment have rubber linings. Moving parts such as the focusing ring and switches are also designed to prevent water and dust from entering. These lenses can therefore be used in harsh conditions without dust and water getting inside.
The lenses are equipped with a rubber ring on the mount to improve their dustproofing and waterproofing characteristics. As the lens is repeatedly mounted and detached, the rubber ring will leave fine abrasion marks on the outside of the camera mount. This will not affect operation.
EF 300mm f/2.8L IS USM
EF 400mm f/2.8L IS USM
EF 500mm f/4L IS USM
EF 600mm f/4L IS USM
EF 400mm f/4 DO IS USM
EF 16-35mm f/2.8L USM
EF 24-70mm f/2.8L USM
EF 70-200mm f/2.8L IS USM
EF 70-200mm f/4L IS USM
Extender EF 1.4x II
Extender EF 2x II
EF 28-300mm f/3.5-5.6L IS USM
EF 16-35mm f/2.8L II USM
APO (APO Lens): In order to attain the highest quality images, the APO lens has been made using special low-dispersion (SLD) glass and is designed to minimize color aberration.
ASP (Aspherical Lens): The aspherical lens complex allows freedom of design, improved performance, a reduced number of component lenses and a compact size.
Conv (APO Teleconverter EX): This lens can be used with the APO Teleconverter EX. It can increase the focal length and will interface with the camera's AE (automatic exposure) function.
DG (DG Lens): These are large-aperture lenses with wide angles and short minimum focusing distances. With an abundance of peripheral illumination, they are ideal lenses for Digital SLR Cameras whilst retaining suitability for traditional 35mm SLRs.
DC (DC Lens): These are special lenses designed so that the image circle matches the smaller size of the image sensor of most digital SLR cameras. Their specialized design gives these lenses the ideal properties for digital cameras, the compact and lightweight construction is an added bonus ! including compact and lightweight construction.
EX (EX Lens): The exterior of this lens is EX-finished to denote the superior build and optical quality, and to enhance its appearance.
HSM (Hyper-Sonic Motor): This lens uses a motor driven by ultrasonic waves to provide a quiet, high speed AF.
IF (Inner Focus): To ensure stability in focusing, this lens moves the inner lens group or groups without changing the lens' physical length.
OS (Optical Stabilizer) Function: This function utilizes a built-in mechanism that compensates for camera shake. It dramatically expands photographic possibilities by alleviating camera movement when shooting by hand held camera.
RF (Rear Focus): This lens is equipped with a system that moves the rear lens group for high speed, silent focusing.
AD (Anomalous Dispersion - Hybrid Aspherical Elements): Lens technology created to help control chromatic aberrations that would otherwise degrade image contrast and sharpness. Anomalous Dispersion glass is a special optical glass that delivers an abnormally large partial dispersion ratio (amount of dispersion at a given wavelength range within visible light) relative to a specific wavelength zone. By combining AD glass elements with elements made of normal glass with different dispersion characteristics, dispersion factors of a specific wavelength can be controlled, resulting in effective compensation of on-axis chromatic aberration on telephoto lenses, or lateral chromatic aberration often associated with wide angle lenses of conventional optical configuration.
ASL (Aspherical): An aspheric lens or asphere is a lens whose surfaces have a profile that is neither a portion of a sphere nor of a circular cylinder. In photography, a lens assembly that includes an aspheric element is often called an aspherical lens.
The asphere's more complex surface profile can eliminate spherical aberration and reduce other optical aberrations compared to a simple lens. A single aspheric lens can often replace a much more complex multi-lens system. The resulting device is smaller and lighter, and possibly cheaper than the multi-lens design. (1)
DI (Digitally Integrated Design): Is the designation Tamron puts on lenses featuring optical systems designed to meet the performance characteristics of digital SLR cameras as well as film cameras. These lenses may be used on cameras with full format (FF) or APS-C sensors (with a crop factor relative to the camera).
Di-II (Lenses for Digital SLR Cameras Only): Lenses are designed for exclusive use on digital cameras with smaller-size imagers (also known as APS-C sensors). These lenses are not designed for conventional cameras and digital cameras with image sensors larger than 24mm x 16mm (not intended to work on Canon EOS-1D for example but does work on Canon EOS 40D, Canon EOS 400D, Canon EOS 30D, Canon EOS 20Da, Canon EOS 350D, Canon EOS 20D, Canon EOS 300D, Canon EOS 10D, Canon EOS D60 and Canon EOS D30).
IF (Internal Focusing): All focusing occurs within the lens, i.e. the lens will not change size as it zooms. Usually a desirable function of a lens.
LD (Low Dispersion - Hybrid Aspherical): Lens technology created to help control chromatic aberrations that would otherwise degrade image contrast and sharpness. LD elements are made from special glass materials with extremely low dispersion indices (characteristics that separate or refract a ray of light into rainbow colors) that effectively compensate for chromatic aberration that is particularly a problem at the telephoto end.
SP (Super Performance): Professional class lens; currently the best lenses made by Tamron for the consumer market.
XR (Extra Refractive Index Glass): Glass having a refractive index of more than 1.69 is called extra refractive or high index glass. This numerical expression compares the speed of light in a transparent medium, like glass, with the speed of light in air. The higher the index number, the thinner a given element will be.
The refractive index – its ability to bend light – plays a critical role in the creation of the power and thickness of an element. Extra Refractive Index (XR) glass bends light more effectively than normal or lower refractive index glass and can therefore compensate for specific aberrations within an optical design.
VC (Vibration Compensation): In lens stabilization - The proprietary VC (Vibration Compensation) mechanism developed by Tamron features a triaxial configuration using three pairs of driving coils and slide balls around the compensator group of the lens’ optical system. Since the compensator lenses are supported with rolling friction of the balls, the response performance is enhanced and the construction is simple, which results in the compactness of the lens. The lens incorporates a highly accurate gyro sensor for detecting hand-shake, which, combined with a 32-bit RISC CPU, offers comfortable anti-vibration effects.
Note About Sources
*Information was gathered and quoted directly from each of the manufactures sites unless otherwise noted. Wikipedia was used to 'check' the assertions of the manufacturers, give relative data such as technical white paper information and dates on creation. This documentation is for information only and the writer makes no assertions to the validity or claims made herein or those made by the manufacturers.
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