Tamron SP AF 17-50mm F/2.8 XR Di II VC

DG (for digital)

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 (for digital)

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

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, highspeed AF.

APO (Apochromatic)

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)

The aspherical lens complex allows freedom of design, improved performance, a reduced number of component lenses and a compact size.

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 highspeed, silent focusing.

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.

IF (Inner Focus)

To ensure stability in focusing, this lens moves the inner lens group or groups without changing the lens' physical length.

VC (Vibration Compensation)

Tamron’s Unique State-of-the-Art In-Lens Image Stabilization System

While other image-stabilization systems can only correct the effects of camera shake in horizontal or vertical planes, Tamron’s VC system uses a tri-axial configuration that employs three pairs of driving coils and low-function ball bearings placed around the shake-compensating optical group to produce, in effect, a free-floating shake compensator. This simple, elegant system is able to compensate for camera shake that occurs in diagonal direction as well as for up-and-down and side-to-side movements. Furthermore, due to its simple, low-friction design it is more responsive and durable than previous systems. TheTamron 28-300mm VC and 18-270mm VC lenses incorporate a highly sensitive and accurate gyro sensor for detecting even the slightest hand shake, and that,combined with a 32-bit RISC CPU and Tamron’s proprietary Algorithms and actuator, provides unequalled real-world performance. The bottom line: Tamron VC provides up to a 4-stop advantage in shooting sharp handheld pictures at slower shutter speeds along with a smooth, stable viewfinder image that is the envy of other shake-control systems. You can expect to see the VC feature built into more Tamron lenses in the future.

USD (Ultrasonic Silent Drive)

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.

By effectively combining these two ultrasonic vibrations, it is possible to convert the energy from the vibrations that produced simple motion into energy known as 'deflective traveling waves', which then moves around the circumference (rotation direction) of the ring.

With the USD, the friction between these deflective traveling waves created on the metallic surface of the stator and the surface of the rotor produce force, causing the rotor to rotate. The focusing ring lens, which is linked to the rotor, is thus moved, creating a fast and smooth auto-focus drive.

PZD (Piezo Drive)

Piezoelectric drive replaces traveling wave energy with more efficient standing wave energy for higher AF performance with less weight and bulk. A vital contributor to compactness, PZD focuses quickly and precisely, assuring sharper results in demanding conditions with speed that captures spontaneous moments crisply—moments that might otherwise be lost to image softness. PZD is exceptionally quiet, making it ideal for nature, live performance shooting, golf and other conditions that demand quiet operation.

SP (Super Performance)

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.

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.

LD (Low Dispersion)

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.)

XLD (Extra Low Dispersion)

A sophisticated XLD (Extra Low Dispersion) lens element made from specialized high-grade glass that has lower dispersive properties than standard LD lenses (where refraction causes the dispersion of white light into spectral hues). The dispersive properties of the XLD lens are at a level similar to fluorite, and in combination with LD elements make for an optimal optical design that delivers best in class resolution with advanced axial chromatic and magnification aberration correction - major inhibitors of image quality enhancement. The result is a lens that delivers sharp contrast and better descriptive performance throughout the entire zoom range.

ASL (Aspherical)

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.

IF (Internal Focusing)

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.

Di-II (Digitally Integrated for Crop Sensor)

Tamron Di-II lenses are engineered expressly for digital SLR cameras with image sensors commonly referred to as APS-C, measuring approximately 24mm x 16mm. Rendering an ideal image circle for APS-C sensors, Di-II lenses also include properties to optimize digital imaging performance.

Di (Digitally Integrated)

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.

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.

A/M (AF/MF)

The ability to switch quickly between auto-focus (AF) and manual-focus (MF) is a great asset in many types of shooting, especially sports and nature photography. This is easily accomplished with Tamron’s ingenious AF/MF system. By simply sliding the focus ring back and forth between the two positions you can select either the AF or MF focusing position. In manual-focus mode Tamron lenses provide smooth, precise manual focusing by turning their wide, well-textured focusing rings.

AD (Anomalous Dispersion For Better Color Correction)

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.)

HID (High Index, High Dispersion Glass)

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.

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.

FTM (Full-Time Manual Focus)

All Tamron lenses have high autofocus precision and are designed to capture subjects easily in almost any situation, yet sometimes a photographer wants to fine tune and make adjustments on the fly. The integration of full time manual focus offers just that: instead of fumbling with switches, photographers can switch from autofocus to manual focus by simply adjusting the focus ring. This feature helps the lens produce impressive results even in telephoto situations where the depth of field is narrow.

VR (Vibration Reduction)

NIKKOR's vibration reducation system helps you achieve sharper, steadier shots by compensating for camera shake when shooting telephoto subjects, dimly lit scenes and other handheld situations--including D-movie shooting. Cameras shake information is detected by the VR sensor of the VR lens unit, which is continually in motion inside the lens, aligning the optical axis with your camera's imagign sensor, thereby reducing image blur and providing the equivalent of shooting at shutter speeds up to three (with VR) or four (with VRII) stops faster, depending on the situation and photographer.

SWM (Silent Wave Motor)

Nikon's original Silent Wave Motor (SWM) converts "traveling waves" into rotational energy to drive the optics used for focusing. The two SWM lens types--ring type and compact type--are specifically chosen to match each lens's specs and design. Any AF-S NIKKOR lens featuring these SWMs delivers extremely smooth, quiet and comfortable auto focusing for general shooting as well as extreme situations, such as sports and wildlife.

N (Nano Crystal Coating)

Originating from Nikon's work in semiconductor manufacturing technology, NIKKOR's Nano Crystal Coat is an antireflective coating that employs an extra-low refractive index coating featuring ultra-fine nano-sized crystal particles. These crystallized particles eliminate reflections inside the lens throughout the spectrum of visible light waves (380 to 780nm) in ways that far exceed the limits of conventional antireflection coating systems. Nano Crystal Coat not only solves ghost effectsc aused by red light, which was ncedibly difficult with previous systems, it also effectively reduces ghost and flare effects caused by light entering the lens diagonally. The result: clearer images.

ED (Extra-low Dispersion)

Nikon was the world's first camera maker to develop ED (Extra-low Dispersion) glass that could minimize prism-caused color dispersion. This low-dispersion ED glass also offers anomalous dispersion characteristics ike calcium flouride crystals, which consequently minimize the secondary spectrum. For lenses with normal optical glass, the longer the focal length, the more difficult to correct the chromatic aberration that causes color fringing. Nikon's ED glass, which effectively compensates for this kind of chromatic aberration, is employed in a wide range of NIKKOR telephoto lenses for superior reproduction. Nikon has also developed Super ED glass to minimize aberration even further.

M/A (Quick Switching from AF to MF)

Simply by rotating a focus ring, M/A mode allows you to switch from autofocus to manual with virtually no time lag. This makes it possible to seamlessly switch to fine manual focusing while looking through the viewfinder.

A/M (Auto-Priority Manual)

This mode enables an easy transition from autofocus to manual during AF operation. However, mode switch sensitivity has eben altered to reduce the possibility of sudden unintentional switching to manual focus while shooting.

IF (Internal Focusing)

With this focusing method, all the lens elements are divided into front, middle, and rear groups, with only the middle group moving to focus.

SIC (Super Integrated Coating)

To enhance the performance of its optical lens elements, Nikon employs an exclusive multilayer lens coating that helps reduce ghost and flare to a negligible level. Nikon Super Integrated Coating achieves a number of objectives, including minimized reflection in the wider wavelength range and superior color balance and reproduction.

AS (Aspherical Lens Element)

Aspherical lenses virtually elminiate the problem of coma and other types of lens aberration - even when used at the widest aperture. They are particularly useful in correcting the distortion in windeangle lenses. In addition, use of aspherical lenses contributes to a lighter and smaller lens design.

RF (Rear Focusing)

With Nikon's Rear Focusing system, all the lens elements are divided into specific lens groups, with only the rear lens group moving for focusing. This makes autofocusing operation smoother and faster.

HRI (High Refractive Index Lens)

With a refractive index of more than 2.0, one HRI lens can offer effects equivalent to those obtained with several normal glass elements and can compensate for both field curvature and spherical aberrations. Therefore, HRI lenses achieve great optical performance in an even more compact body.

CRC (Close Range Correction)

The Close-Range Correction system is one of Nikon's most important focusing innovations. Using an innovative floating element design, each lens group moves independently to achieve superior performance at close distances.

DX (Crop Sensor)

In digital cameras, the camera's format refers to the size of its image sensor. Nikon makes a DX-format sensor and an FX-format sensor. The DX-format is the smaller sensor at 24x16mm; the larger FX-format sensor measures 36x24mm which is approximately the same size as 35mm film.

Different NIKKOR lenses are designed to accommodate the different camera sensor sizes. In the case of DX cameras with their smaller sensors, corresponding DX lenses have been designed. The DX designation can be found in the lens name, i.e. AF-S DX Zoom-NIKKOR 12-24mm f/4G IF-ED. These lenses are smaller and lighter in weight and address the market's need for affordable, high-performance lenses with a variety of focal lengths and zoom options.

The DX sensor makes possible the production of lighter, smaller cameras, but because it covers a smaller portion of the image projected by the lens, a 1.5x crop factor (so called because the smaller sensor crops the image compared to an image from a 35mm film frame) is introduced. This means, for example, a 24mm lens on a DX sensor camera will provide an approximate 36mm view.

The FX sensor, with more "light gathering" area, offers higher sensitivity and, generally, lower noise. There is, of course, no crop factor present with the FX sensor.

DX cameras have the added benefit of being able to use both DX and non-DX NIKKOR lenses-those lenses without the DX designation in their names.

D-Type

A NIKKOR lens that sends distance information to the microcomputer of a dedicated Nikon camera. D-type lenses can be distinguished by a model name in which the letter D follows the maximum f/number.

G-Type

G-type NIKKOR lenses have no aperture control ring and are intended for use on Nikon D-SLRs that allow the lens aperture to be adjusted via the camera's command dial.

AF-S (Autofocus Silent)

Focusing is driven by a "Silent Wave" motor in the lens instead of the focus drive motor in the camera. AF-S lenses focus faster than standard AF-NIKKORs and almost completely silently.

Will autofocus even on Nikon bodies without a built-in focus motor.

DC (Defocus Control)

A lens which allows the photographer to control the degree of spherical aberration in the foreground or background by rotating the lens' DC ring.

D (Digital)

A lens optimized for use on more demanding digital sensors. Full frame.

DX (Digital Crop)

Designed specifically for crop sensors.

FX (Full Frame)

Designed with modern digital full-frame cameras in mind.

AS (Aspherical Optics)

A standard lens is made up of a combination of spherical lens elements. Individual “lenses” within the lens are commonly referred to as “elements”. A spherical element has an even curve to the surface of the glass. However, there can be problems with such elements; light entering the center of the lens and light entering at the edge may not be perfectly focused at the same point. This is called spherical aberration. More advanced computer assisted optical designs are creating lenses with more spherical elements. More spherical elements within a lens means a greater risk of spherical aberration having a negative impact on optical quality.

Wide-angle zoom lenses and wide-angle lenses with large apertures are especially at risk for spherical aberration.

To eliminate spherical aberration, Tokina employs aspherical all-glass elements in many of its optical designs to correct this problem. The aspherical shaped surface of the lens element focuses light rays entering both the center and edge of the element correctly at the film plane for an accurately focused image. In addition to correcting spherical aberration, these elements fully correct light quantity and distortion at the edge of the image and provide excellent results when used in combination with a floating element design.

Through a close collaboration with Hoya Corporation, the world’s largest optical glass manufacturer, Tokina has succeeded in producing high quality precision molded all glass elements with a greater aspherical shape than any other lens manufacturer. This technique is unparalleled in its technological sophistication and precision.

F&R Aspherical (Front & Rear)

This lens, the AT-X 235 AF PRO encompasses Tokina’s new F&R aspherical molded glass elements of an exceptionally large 50 mm diameter in the front and 20 mm diameter element at the rear. The 50 mm front element is one of 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 across the image area.

SD (Super Low Dispersion)

When standard optical glass is used in telephoto lenses, a phenomenon called chromatic aberration can occur. Chromatic aberration is the inherent tendency for glass to disperse (separate) a ray of light into the colors of the rainbow. The rainbow effect created by a glass prism is the most dramatic demonstration of chromatic aberration. In lenses, it is much less pronounced, but still creates slightly out of focus colors, akin to an “optical noise” that has a negative impact on the quality of the picture. To eliminate chromatic aberration, Tokina employs expensive, special glass material having super- low dispersion (SD) properties.

Lenses in the Tokina line-up with the SD mark incorporate these Super-Low Dispersion glass elements, minimizing the secondary spectrum or optical noise caused by chromatic aberration.

HLD (High Refractive, Low Dispersion)

Tokina’s wide-angle and standard zoom lenses feature a higher quality of optical glass known as Tokina HLD (High-refraction, Low Dispersion) glass. Having higher refractive index and lower dispersion properties, HLD glass is far less likely than standard optical glass to create lateral chromatic aberration, which is often a problem with conventionally designed wide-angle lenses.

MC (Multi-Coating)

Reflections off the surface of lens elements are the enemy to any photographer and to every lens manufacturer. They are reduced or eliminated by bonding multiple layers of a transparent anti-reflection chemical to the surface of the glass. Tokina has developed and perfected a unique coating technique for all of its optics so that they will maintain faithful color reproduction and render clean, sharp images.

FE (Floating Element)

When designing a lens, Tokina calibrated its astigmatism at all points between minimum focus distance and infinity so that it will give the best image results at all settings. However, when there are large differences between the focus limits, effect calibration is not possible. A floating element system incorporates optical elements that move in proportion to the focus setting of the lens. This allows astigmatism to be corrected. Many Tokina lenses employ floating element systems to provide optimum correction of astigmatism from minimum focus distance to infinity.

IF (Internal Focus)

The two most used methods of focusing a lens are either the complete straight forward movement of lens elements (used mainly with single focal length lenses) or the rotation of the entire lens barrel group (used mainly with zoom lenses). The internal focusing system used by Tokina move each element group within the lens, but does not change the overall length of the lens. This is especially useful with telephoto designs.

The internal focusing system has a number of advantages including;

• Faster focusing
• Improved handling due to fewer movements near the center of gravity
• More compact lens designs
• Superior use of filters because the barrel with the filter thread does not rotate.

IRF (Internal Rear Focus)

By movement of rear elements only: AT-X 300 AF PRO

FC (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.

The manual focusing ring can move (be snapped) back and forth between an AF and MF position. When the focusing ring is forward in the AF position, it is not engaged to any of the internal focus gearing and will turn freely. Without the added weight of the metal ring the camera can auto focus the lens more quickly and smoothly.

For manual focus, simply rotate the focus ring all the way to one side or the other on the focus travel, either infinity or it’s closest focusing distance, then pull back (towards the mount plate) on the manual focus ring. While pulling back, rotate the ring from one side of the focus travel to the other. When the gears align, the focus ring will snap back into the MF position and the lens can be focused manually.

To return the manual focus ring to auto focus mode, simply snap the ring forward from any point.

IRF (Internal Rear Focus)

A refinement of the focus clutch mechanism has been incorporated in the AT-X 280 AF PRO Nikon and Canon mount, so that now the lens’ focus ring can be snapped back to the manual focus position at any time, from any position. This improvement means it is not necessary to change the AF/MF switch (on the body with Nikon or the lens with Canon) every time the lens is changed from auto focus to manual focus mode.