SP AF17-50mm F/2.8 XR Di II VC LD Aspherical [IF]

This lens covers the extremely popular 17-50mm focal length range (equivalent to 26-78mm in the full-frame 35mm format*) making it extremely versatile. It delivers impressive sharpness and striking contrast over its entire range of focal lengths and apertures. this lens delivers a fast f/2.8 aperture over its entire range of focal lengths for maximum creative flexibility. At its maximum aperture of f/2.8 it produces beautiful images enhanced by shallow depth of field and excellent bokeh (i.e. smooth, natural transitions in the out-of-focus areas of the image). Equipped with Tamron’s state-of-the-art, tri-axial Vibration Compensation (VC) image stabilisation mechanism, which controls the effects of camera shake, this lens provides more opportunities for sharp handheld photography at the slow shutter speeds needed when shooting in low-light conditions (e.g. night or indoor scenes), dramatically enhancing the user’s level of photographic freedom. Three compound aspheric elements, special LD glass, and BBAR coatings ensure superb correction, colour fidelity, and freedom from flare. A minimum focus distance of 0.29m (11.4 inches) offers exciting close-up opportunities.

* Using a conversion value of 1.55x.

Super Performance series

Performance takes priority for superb image quality

Vibration Compensation

Compensates for camera blur on long shutter speeds – for sharp images in much lower light

Tamron’s unique VC mechanism uses a proprietary actuator and algorithms to deliver an extremely stable viewfinder image with excellent tracking. The mechanism employs a tri-axial system in which three driving coils move internal optical components within the VC lens electromagnetically. The VC lens elements are held in place only by contact with three ball bearings – which in the latest Tamron VC lenses are ceramic – achieving smooth movement with minimal friction. The simplicity of this mechanical structure is also one of the secrets of Tamron’s compact lens sizes.

A fast zoom lens with the added advantages of Vibration Compensation

One of the greatest photographic challenges is creating natural-looking images in lower light levels – indoors, in deep shadow or in the evening. Photographers know that a ‘fast’ lens – one with a wide maximum aperture – extends their creativity in this respect, because the increased amount of light transmitted to the sensor at f/2.8 allows a longer shutter speed at the same ISO setting. It avoids:

• The time and intrusiveness of setting up a tripod to stabilise the camera and increases the spontaneity and flexibility of shooting.
• Moving to a higher ISO setting, where noise or ‘digital grain’ reduces image quality.
• Using flash to ‘freeze’ blur from camera shake, which not only results in a less natural-looking image but can also be intrusive during shooting.

Equipping a fast lens with VC technology extends the range of handheld shutter speeds, and all the consequent advantages, even further. Even when shooting in light levels where handheld photography is generally possible, combining the fast f/2.8 maximum aperture of this lens with the VC image stabilisation permits dramatic blur from subject movements – previously requiring the set-up of a tripod.

Compact size with a filter thread of Ø72mm, while delivering both a large f/2.8 diameter and VC

The addition of an image stabiliser tends to increase the size of a lens. As this lens is a large-diameter f/2.8 zoom, the optical image stabilisation system is also relatively large compared with other VC models. However, through improvements to optical, mechanical and VC designs, the filter thread is a compact 72mm.

Zoom-lock mechanism

Useful when carrying the lens/camera over the shoulder

Another original Tamron mechanical engineering concept is the zoom-lock mechanism, which prevents the weight of the lens barrel from extending the lens when carried on the camera pointing downward. This eliminates the danger of accidentally knocking the lens while walking around and enhances responsiveness in the field. Simply zoom the lens out to its widest focal length and use the sliding zoom-lock switch to lock the barrel in place.

Internal Focusing

Focusing elements inside the optical design make for better handling

In many lenses, the front elements move back and forth to alter the focus distance. With an internal focusing (IF) mechanism, the focusing elements are inside the optical design. Because the front lens elements remain static, the lens’ actual length does not change. This provides several benefits both to the image and during photography:

• The barrel is not subject to stray light entering from external helicoids that can adversely affect image quality
• A non-rotating front filter thread makes it easier to use filters such as graduated filters and polarisers
• A flower-shaped lens hood will remain in the correct position to most effectively shield the lens from stray light
• Better balance and more predictable handling because the lens length does not change during focusing
• Generally, a much closer minimum focusing distance throughout the zoom range
• Improved optical performance by minimising loss of illumination at the corners of the image field (vignetting)
• Suppression of other aberrations that become more troublesome at different focusing positions.

Integrated focus cam optimises internal focusing

Tamron’s Integrated Focus Cam is a precision mechanical component that optimises the co-ordinated movement of the Internal Focusing (IF) system with the Multiple Cam Zoom Mechanism. This ingenious mechanism ensures accurate and seamless positioning of all the internal elements within the lens and coordinates them with the external zoom and focus controls.

Extra Refractive Index

More compact lenses with superior image quality

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 minimising optical aberrations. With its superior light-bending power, XR glass 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. XR glass is costlier than conventional glass but it yields enhanced optical power distribution, making the innovative XR lens designs possible.

Low Dispersion

Sharpens edges by reducing ‘colour fringing’

Chromatic aberration occurs when a lens element refracts different wavelengths of a ray of light – its rainbow colours – at very slightly different angles. This results in the ‘colour fringing’ that reduces the sharpness of an image. LD elements are made from special glass materials with extremely low dispersion indices (i.e. the refraction of a ray of light into rainbow colours is extremely narrow). Thus they effectively compensate for chromatic aberration at the centre of the field (on axis), a particular problem at long focal lengths (the telephoto end of the zoom range), and for lateral chromatic aberration (toward the edges of the field) that often occurs at short (wideangle) focal lengths. Although costly, LD glass materials result in clear, vivid image quality.

Aspherical

Far superior image quality – while reducing lens size and weight

Tamron uses several hybrid aspherical lens elements in its lenses bearing the Aspherical designation. The benefits are two-fold: first, their non-spherical shapes virtually eliminate spherical aberration and image distortion. Second, as one hybrid aspherical lens element can take the place of multiple elements without compromising performance, they allow the lens to be much more compact. As a result, these innovative optics have played a crucial role in delivering uniformly high image quality across all apertures and focal lengths of extraordinarily compact ultra-zoom lenses.

Broad-Band Anti-Reflective coating

Cleaner, crisper images without flare or ghosting

The latest BBAR (Broad-Band Anti-Reflection) multi-layer coatings reduce reflection from the lens, ensuring excellent performance in all photographic conditions. These coatings enhance light transmission in both short and long wavelengths. Internal coatings have also been applied to all the cemented surfaces of lens elements, providing sharpness, optimum colour reproduction and excellent colour balance.

*Values are for the Nikon-mount model.