SP AF28-75mm F/2.8 XR Di LD Aspherical [IF]

This lens utilises the XR size-reduction technology developed by Tamron for its “super-zooms” to create a fast standard zoom lens of an almost unbelievably compact size for a lens of this type. With a filter diameter of 67mm, maximum diameter of 73mm, length of only 92mm and weighing only 510g, the image of fast standard zooms as heavy and cumbersome is turned on its head. As such, this lens represents the first in a new category: a fast standard zoom that can be used comfortably as the lens regularly attached to a camera body. In addition, to meet the needs of this dual-format (film and digital) world, the optical system of the lens* is designed to provide optimum performance when used with the latest digital SLR cameras. * Di: “Digitally integrated design”, Tamron’s designation for lenses featuring optical systems designed to meet the performance characteristics of digital SLR cameras while covering the image circle of 35mm film.

Super Performance series

Performance takes priority for superb image quality

Form and texture that embodies the high-performance, high-precision qualities of the SP series

This lens features the two gold metal rings that symbolise the SP series, and other design elements that boost its looks. The covering of the zoom and focus rings improve grip. A sleek burnished-black finish on the lens barrel imparts a further touch of refinement. Tamron has also improved the readability of important imprinted information on the lens such as the distance scale and f-numbers.

An innovative combination of optical technologies

The revolutionary use of XR (eXtra Refractive index) glass enables reduction in size while at the same time compensating for aberrations, resulting in the optimisation of overall optical power distribution. Now compactness and light weight are combined with high SP-characteristic performance in this unprecedented “standard zoom” lens. Through an optimal arrangement of four hybrid aspherical elements, compositional capabilities have been maintained while achieving a reduction in the dimensions of the overall optical configuration. The use of three LD (Low Dispersion) elements ensures superb image quality.

Structural innovations enable significant downsizing, reduction in zoom torque and torque fluctuation

Thanks to mechanical innovations that enable a very complex structure to be compressed into a compact barrel, the maximum lens diameter has been downsized considerably to a mere 73mm (2.9″). Handling is enhanced with the reduction of zoom torque and improved torque fluctuation. Tamron has also implemented advancements in manufacturing technology, enabling the production of lighter, stronger and higher precision parts.

Minimum object distance of just 0.33m (13″) over the entire zoom range, and maximum magnification ratio of 1:3.9

This lens boasts a minimum object distance (MOD) of just 0.33m throughout the zoom range. At its telephoto end, macro shooting is available with a maximum magnification ratio of 1:3.9. While the MOD of the earlier SP AF28-105mm f/2.8 changed according to focal length setting (0.5m at 28mm and 105mm, 0.44m at 70-85mm), improvements to the optical and structural design have enabled the reduction in the SP AF28-75mm’s MOD to a constant 0.33m.

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.

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.

Flower-shaped hood is supplied with the lens to shield stray light

Included as a standard accessory, the flower-shaped hood matches the rectangular shape of the image sensor to most effectively block the interference of superfluous light rays entering from outside the borders of the image area, helping to ensure sharp, clear, flare-free images with crisp detail in the shadow areas.

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.

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.

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.

*Values given are for Nikon mount.