- APO - Apochromatic lens element(s)
An Apochromat lens, which keeps color aberration to a minimum, using Special Low Dispersion glass is called an APO series lens at Sigma. As the refractive index of glass depends on the wavelength of the light, color aberration occurs when different colors form images at different points. This problem often occurs with telephoto lenses. In the case of normal optical glass it can only be corrected for two primary spectral colors by combination of low dispersion convex and high dispersion concave lenses. Sigma Apo lenses use SLD (Special Low Dispersion) or new ELD (Extraordinary Low Dispersion) glass to offer superior sharpness, high contrast and color correction by minimizing the chromatic aberration.
- Aspherical lenses
Many Sigma lenses make effective use of Aspherical lens elements. This technology allows one Aspherical lens element to perform the functions of two or more conventional spherical elements, thus allowing the lens to be made more compact and lightweight, while retaining high levels of performance. In the 20mm f/1.8, 24mm f/1.8, 28mm f/1.8 EX DG lenses, for example, these Aspherical elements eliminate the sagittal coma flare that accompanies large lens diameters. They effectively suppress the flare. In zoom lenses, where the wide angle range is extended - such as the 15-30 f/3.5-4.5 EX DG - distortion control can be enhanced by the use of Aspherical elements.
- OS - In lens 'Optical Stabilization', analogous to Nikon VR or Canon IS
- HSM - 'HyperSonic Motor', in-lens ultrasonic motor, analogous to Pentax SDM, Nikon AF-S or Canon USM.
The HSM motor is driven by ultrasonic waves and it makes auto focusing, precise, silent and high-speed.
- EX - 'Excellence', professional series.
The Excellent features of these Sigma lenses such as new optical and mechanical design concept, superior performance, perfect handling, ultra compact design, durability etc., are symbolized by the EX mark. These professional type lenses are distinguished by their the distinctive EX finish and EX logo on the lens barrel.
- DG - Coatings optimized for Digital SLRs, still usable on 35mm or full frame.
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.
- DC - Lenses for DSLRs featuring APS-C size sensors only
These are special lenses designed so that the image circle matches the smaller size of most digital SLR cameras. Their specialized design gives these lenses the ideal properties for digital cameras, including compact and lightweight construction.
- DF - 'Dual Focus', lens features clutch to disengage focus ring when in AF mode
- HF - 'Helical Focusing', front element of lens does not rotate (for when using circular polarizing filters)
- AD - Anomalous dispersion
Anomalous dispersion (AD) glass is a special type of optical glass that is used to achieve more precise control of chromatic aberrations, thereby enhancing overall imaging performance. Glass of this type provides an abnormally large partial dispersion ratio (amount of diffraction) for light of specific wavelength ranges (colors) within the visible spectrum. By combining AD glass having these special characteristics with elements made of normal glass having different dispersion characteristics, it is possible to control the dispersion factors of a specific wavelength. This enhanced level of control results in much lower levels of on-axis (central) chromatic aberration for telephoto lenses (or zooms used at tele-photo settings) and a significant reduction of lateral (peripheral) chromatic aber-ration for wide-angle lenses (or zooms used at wide-angle settings.)
- ASL - Hybrid Aspherical Elements
Tamron uses several hybrid aspherical lens elements in many lenses bearing the Aspherical designation. These innovative optics allow us to achieve the ultimate in image quality, and at the same time produce lenses that offer remarkable zoom ranges in extraordinarily compact packages. By perfecting theses cutting-edge advances for series production, Tamron has advanced the state of optical design, and virtually eliminated spherical aberration and image distortion from the high-power-zoom series.Through the effective application of Hybrid Aspherical Technology, one lens elemen tcan take the place of multiple elements without compromising performance. This is what allows us to produce remarkably compact long-range lenses that deliver a uniformly high level of image quality at all focal lengths and apertures.
- Di - 'Digitally Integrated', featuring coating optimized for digital SLRs, but still usable on 35mm or full frame.
Di (Digitally Integrated Design) is a Tamron designation that applies to lenses that have been optimized for digital capture using advanced multi-coating techniques and optical designs that assure excellent image quality across the entire picture field. Because of these characteristics, Di lenses provide outstanding performance on cameras with full-frame and APS-C format sensors as well as on 35mm film.
- Di II - Lenses for DSLRs with APS-C sized sensors only.
Di-II is the designation Tamron applies to lenses designed for exclusive use on digital SLR cameras with APS-C format image sensors. All Di-II lenses are optimized to meet the performance characteristics of this popular class of cameras, providing maximum resolution concentrated within the image field and assuring that light rays at the edge of the frame reach the sensor at favorable angles, thereby minimizing peripheral light falloff. In addition, all lenses bearing this designation incorporate effective measures to increase light transmission and eliminate ghosting and flare, which are particularly noticeable with digital cameras. Tamron’s advanced multi-coatings are applied not only to external and internal lens surfaces, but also to surfaces in between cemented lens elements. Finally, Di-II lenses are offered in a wide array that includes the focal length ranges most desired by DSLR users.
- FEC - Filter Effect Control
The Filter Effect Control is designed to rotate the filter to the desired position while the hood is attached. This is accomplished by turning the FEC ring that in turn rotates the portion of the filter mount where the filter is mounted.
- HID - High Index, High Dispersion
The use of HID (High Index, High Dispersion) glass elements in a lens can also be used to minimize on-axis and lateral chromatic aberrations that are the greatest hindrances to achieving high image quality. HID glass is another tool in the lens designer’s arsenal that has allowed Tamron to design and produce complex lenses such as long-range zooms that are conveniently compact and lightweight, and deliver outstanding performance.
- SP - 'Super Performance', professional lenses.
Tamron SP (Super Performance) series is a line of ultra-high-performance lenses designed and manufactured to the exacting specifications demanded by professionals and others who require the highest possible image quality. In creating SP lenses Tamron’s optical designers put their foremost priority on achieving superior performance parameters-they are all designed to a higher standard with little regard for cost constraints. As a result, Tamron lenses bearing the SP designation feature impressive and innovative designs that have established an enviable reputation for excellence among those knowledgeable photographers that demand the very best.
- IF - 'Internal Focus'
Internal focusing (IF) provides numerous practical benefits to photographers including a non-rotating front filter ring that facilitates the positioning of polarizing and graduated filters, and more predictable handling because the lens length does not change during focusing. Even more important, Tamron’s Internal Focusing (IF) system provides a much closer minimum focusing distance (MFD) throughout its entire focusing range. In addition, IF improves optical performance by minimizing illumination loss at the corners of the image field, and helps to suppress other aberrations that become more troublesome at different focusing positions.
- LD - 'Low Dispersion' elements.
Low dispersion (LD) glass elements in a lens help reduce chromatic aberration; the tendency of light of different colors to come to different points of focus at the image plane. Chromatic aberration reduces the sharpness of an image, but glass with an extremely lowdispersion index, has less of a tendency to separate (defract) a ray of light into a rainbow of colors. This characteristic allows the lens designer to effectively compensate for chromatic aberration at the center of the field (on axis), a particular problem at long focal lengths (the telephoto end of the zoom range), and for lateral chromatic aberration (towards the edges of the field) that often occurs at short focal lengths (the wide-angle end of the zoom range.)
- XR - Extra Refractive Index glass.
XR (Extra Refractive Index) glass can bend light rays at steeper angles, thereby decreasing the physical length of the lens while enhancing imaging performance by minimizing optical aberrations. This has allowed Tamron to develop a line of shorter, smaller-diameter, lighter lenses without sacrificing lens speed, and actually upgrading image quality compared to older designs. XR glass is costlier than conventional glass but it yields enhanced optical power distribution, making possible many of the outstanding and innovative lens designs that bear the XR designation. XR glass, with its superior light-bending power, makes it possible to design a short-barrel lens with the same light-gathering ability (aperture value) as a long-barrel lens-even with a smaller lens diameter. By using this principle Tamron has been able to shorten the length of the entire optical system and produce lighter, more compact lenses of the same speed, and also to provide greater zoom ranges in lenses that are much more convenient to carry and hand-hold.
- VC - 'Vibration Compensation', in lens stabilization analogous to Nikon VR or Canon IS
Handheld camera shake is the leading cause of blurry and unsharp pictures. Several leading companies now make lenses with built-in optical image-stabilization systems that sense the amplitude and direction of the shake and compensate by moving optical groups within the lens.
- USD - Tamron’s USD works with the high-frequency ultrasonic vibrations that are produced by a ring called a ‘stator’. Energy from the vibrations is used to rotate an attached metallic ring known as the ‘rotor’. Piezoelectric ceramic, an element that produces ultrasonic vibrations when voltage of a specific frequency is applied is arranged in a ring formation on the stator. This electrode configuration of piezoelectric ceramic causes two ultrasonic vibrations to occur in the stator.
- ZL - Zoom Lock
Another original Tamron mechanical engineering concept is the Zoom Lock (ZL), a simple convenience feature that prevents undesired extension of the lens barrel when carrying the camera/lens unit on a neck strap.
- AT-X - 'Advanced Technology-Extra' - lenses that are manufactured without compromise, using the most advanced design and fabrication technologies available
- F&R - the largest aspherical elements being employed in optical designs today. These give outstanding performance with very even illumination in the corners and correction of spherical aberration
- SD - Super Low Dispersion - to eliminate chromatic aberration, Tokina uses special glass material having super - low dispersion (SD) properties.
- HLD - High-refraction, Low Dispersion. Having higher refractive index and lower dispersion properties, HLD glass is far less likely than standard optical glass to create lateral chromatic aberration.
- Multi-Coating - Reflections off the surface of lens elements are reduced or eliminated by bonding multiple layers of a transparent anti-reflection chemical to the surface of the glass
- Floating Element System – many Tokina lenses employ floating element systems to provide optimum correction of astigmatism from minimum focus distance to infinity.
- IFS - Internal Focus System - The internal focusing system used by Tokina move each element group within the lens, but does not change the overall length of the lens.
- Focus Clutch Mechanism - Tokina AT-X PRO series lenses all feature the patented 'Focus Clutch' Mechanism for switching the lens between auto focus and manual focus modes.
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