Tamron SP AF17-35/2.8-4 Di LD Aspherical (IF) Review
The Tamron SP AF17-35/2.8-4 Di LD Aspherical (IF) is a fast, general purpose lens for both digital and film cameras. On a film camera the 17-35 mm range covers a lot of applications from landscapes and photojournalism to travel and environmental portraits. On a typical APS-C digital camera, such as the Canon EOS 20D, it has the same field of view as a 27-56mm lens would on a full frame 35mm camera. This is a range typically used for both landscape work and photojournalism (street shooting).
Tamron SP AF17-35/2.8-4 Di LD Aspherical (IF) is a Tamron "Di" lens. Di lenses designed with digital SLRs in mind and Tamron say that they have higher resolution, better control of flare and ghosting, less light fall-off and lower chromatic aberration than earlier designs.
Note that the Tamron SP AF17-35/2.8-4 Di LD Aspherical (IF) Review has full frame 35mm coverage. Just because it's designated as a "Di" (digitally optimized) lens doesn't mean that it has reduced frame coverage like, for example, the Canon EF-S series lenses. You can use this lens on an APS-C sensor SLR (e.g. Canon EOS 20D) or on a full frame 35mm film body.
The lens solidly constructed with a low reflectivity black finish and a rubberized zoom control. It comes with a "petal" style detachable lenshood. The barrel material appears to be plastic.
The zoom cannot be locked, but I saw no "creep" at any focal length setting, even with the lens pointing vertically up or down.
Focus can be switched between AF and MF with a small switch on the left, near the lens mount. Manual focus is smooth with about a 90 degree rotation of the rubberized focus ring from 0.3m to infinity. There are no depth of field scales and no IR focus identification mark. It's marked with focal lengths of 17mm (maximum aperture f2.8), 20mm (maximum aperture f3.2), 24mm (maximum aperture f3.5), 28mm (maximum aperture f3.5) and 35mm (maximum aperture f4)
Focus speed is pretty good. It takes the Tamron SP AF17-35/2.8-4 Di LD Aspherical(IF) about 0.5 seconds to go from infinity to 0.3m. Focusing isn't silent but it's not really noisy and certainly not a problem.
The lens extends slightly (less than 1cm)when zoomed, but does not change length on focusing (it's internal focus - IF) and the front of the barrel does not rotate when the lens is zoomed or focused. However the focus ring does spin during autofocus, so keep your hands away from it.
The Tamron SP AF17-35/2.8-4 Di LD Aspherical (IF) uses two types of special optical elements as shown above. LD (low dispersion) glass is used to minimize chromatic aberration and aspherical elements are used to minimize aberrations like spherical aberration which become troublesome in fast wideangle lenses.
The lens has a close focus distance of 0.3m which gives a maximum magnification of 1:5.4 at 35mm.
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