Although the Di technology was developed for improved performance with digital SLRs, the 17-35mm zoom produces excellent results with film cameras as well. Most of my 35mm slides are razor sharp across the entire frame and exhibit remarkable sharpness, clarity, contrast, and resolution of fine detail. (EOS-3; HOYA polarizer; at 17mm; f/8; Fujichrome Velvia 100F film.) Photos © 2004, Peter K. Burian, All Rights Reserved

Lens Characteristics
For a wide aperture ultra-wide zoom, the 17-35mm Di is quite compact and also lightweight thanks to the use of engineering plastics said to "excel in dimensional stability and strength." (The lens mount is made of metal, however.) Nicely finished in matte black with white distance and focal length scales, the barrel features a rotary zoom mechanism, wide, rubberized focus and zoom rings, both well damped, with enough friction for convenient operation. Although the focus ring rotates during autofocus operation, response is fast and fairly quiet thanks to internal focusing; the front element does not rotate so the effect of a polarizing filter does not shift. Because of the wide maximum aperture, the cameras' autofocus systems remained reliable even while shooting night scenes in Las Vegas.

When tilted upward to include most of the New York New York series of facades in Las Vegas, the lens produced significant linear distortion. Vertical lines seem to converge or lean inward out of plumb. Of course, this "keystoning" is a characteristic of all short focal length lenses and occurs whenever certain subject elements (such as the base of the buildings) are closer to the lens than others. For images with "normal" perspective, simply position the camera back so it's perfectly parallel with the subject. Granted, you may find a bit of barrel distortion (bowing outward of lines near the edge of the frame) in full frame digital images or 35mm slides and negatives made in the 17-20mm range. This is common with most ultra-wide angle lenses but in my estimation, it's problematic only in formal architectural photography.

The 17-35mm Di zoom focused very quickly, particularly when used with a camera with an advanced autofocus system. That combination made the lens ideal for capturing a nearby action subject or a fleeting moment without the frustration produced by some equipment that often hunts for focus. (EOS-1Ds; at 35mm; f/4.5 at 1/1000 sec; ISO 50; HOYA polarizer; image cropped slightly.)

Performance Evaluation
As noted in our sidebar, the 17-35mm Di zoom incorporates both aspherical and low dispersion glass for optimum image quality at all focal lengths. This high tech optical formula pays dividends in image quality as I confirmed with a 35mm EOS-3 and a digital EOS 10D and EOS-1Ds. At all focal lengths, the lens produced images and color slides with very high contrast, sharpness, color fidelity, clarity, and remarkable resolution of intricate detail at every aperture from f/2.8 to f/11. This consistency indicates a particularly effective optical design. Because there was no need to stop down to optimize image quality, I felt confident shooting at f/2.8 or f/4 on dark, overcast Oregon days, allowing me to use an lSO 100 setting with the EOS 10D for optimal image quality.

Particularly in the 17-30mm range of focal lengths, and especially at f/8, image quality is superlative with edge sharpness matching central sharpness. Flare was very well controlled, a real benefit on sunny days in the Valley of Fire State Park, even in extreme sidelighting. In all of my images, brightness is consistent across the entire frame, at all focal lengths, by one stop down from the maximum aperture. My best digital images made for exhibition quality 11x17" ink jet prints and my Velvia 100F slides are also technically exceptional.

The 17-35mm zoom rendered this highly reflective subject--photographed with a digital SLR camera with a highly reflective sensor--without any evidence of flare, thanks to the extensive use of new multilayered coatings. (EOS-1Ds; ISO 50; f/8; at 19mm; HOYA polarizer.)

Final Assessment
I considered this 17-35mm Di lens to be an ideal ultra-wide zoom with the EOS-3 and the EOS-1Ds with its full frame CMOS sensor. At the shortest focal lengths, it allowed me to include a vast panoramic scene in a single image and in close focusing it produced more powerful wide angle effects than my 20-35mm zoom. The expanded spatial perspective at 17mm makes nearby rocks seem to loom while distant subjects seem to recede for a greater sense of depth in a two-dimensional photo. When mounted on the EOS 10D, with a smaller sensor, the effective focal lengths were 27.2-56mm in terms of the effective angle of view, less useful for dramatic effects. Still, this lens would be a suitable "normal" zoom for any digital SLR with an APS-size sensor, more useful than a 28-80mm zoom that cannot produce true wide angle images with such cameras.

A

B

When used with a 35mm SLR camera, the 17-35mm Di zoom produces images with a super wide angle of view (Photo A) at the shortest focal length. The angle of view is narrower (Photo B) when used with a digital SLR camera with a small sensor but the images retain a wide angle. (EOS-3; f/11; HOYA polarizer; Fujichrome Velvia 100F film; vignetting caused by polarization of the sky; 35mm slides used for illustration of effective angle of view.)

This "Digitally Integrated" zoom allowed me to make many images of professional caliber. But did it produce better results than conventional lenses when used with the EOS 10D? As in my review of the previous two Tamron Di lenses, I cannot provide a definitive conclusion. Frankly, that determination could only be made with a fully equipped optical lab. It would require scientific comparison testing with several similar ultra-wide angle zooms, with and without the Di technology.

Nonetheless, I can offer the following assessments of the Tamron SP AF17-35mm f/2.8-4 Di LD Aspherical [IF] zoom. It's superior in most respects to the older SP AF20-40mm f/2.7-3.5 Aspherical [IF] zoom that I used frequently for stock photography for several years. In fact, this new Di lens is probably the best ultra-wide zoom that Tamron has ever produced. Whether you own a 35mm or digital SLR camera, check out this lens if you're a serious photographer who wants the latest technology and appreciates the creative and problem-solving benefits of a 17-35mm zoom.

For more information, visit Tamron's website at: www.tamron.com.

Peter K. Burian, a free-lancer stock photographer and long-time "Shutterbug" and eDigitalPHOTO" contributor, is the author of a new book, "Mastering Digital Photography and Imaging" (Sybex, March 2004). Covering all aspects of the topic--the technology, equipment, and techniques--this book provides 300 pages of practical advice for photo enthusiasts.

Even at wide apertures the "Digitally Integrated" 17-35mm Di zoom produces images with even brightness across the frame, high resolution of fine detail, and great sharpness. There's no need to stop down to small apertures to optimize image quality as with some conventional lenses. (EOS 10D; at 17mm setting for 27.5mm equivalent focal length; at f/4; ISO 100.)

The Value Of Digital Optimization
The vast majority of autofocus lenses were designed to produce optimum results when used with 35mm SLR cameras. Although they can also be used with digital SLR bodies, some lenses do not produce the same level of quality on the new, high tech cameras. Particularly at wide apertures, internal reflections can cause more serious flare, "ghosting" (reflections in the shape of the lens diaphragm), low contrast, as well as light falloff, resulting in darkening at the edges of the frame.

Most of these problems occur because CMOS and CCD sensors are highly reflective. When light reflects from the sensor (or from the protective glass cover), it bounces to the rear element of the lens creating flare that can degrade image contrast and apparent sharpness. In most lenses for 35mm systems, the rear element is not coated with multiple layers of anti-reflective compounds because the matte film surface produces only diffused reflections. The stronger reflections in a digital camera can degrade image quality to a greater extent, calling for additional anti-reflection countermeasures. In the Di lenses, a new type of multilayered coating is applied to more lens elements (including the rear element) to minimize internal reflections for images with snappier contrast.

There's another characteristic of CCD and CMOS chips that must be considered when designing a digitally optimized lens: The sensors produce the best results with light that strikes all pixels at a 90Þ angle. With many conventional lenses, particularly ultra wides, the light reflected from the subject strikes the image plane at an increasingly oblique angle as you move toward the edges of the frame. This can cause a darkening at the corners of a digital image and occasionally, lower resolution, especially noticeable in wide angle shots made at wide apertures. (At f/8 and smaller apertures, neither problem is significant.) While some digital camera manufacturers have used light altering systems to help minimize the effect, not all do, and some do more successfully than others.

When designing the 17-35mm Di zoom, the engineers specified three aspherical elements to correct the angle of light plus other measures for increasing corner "luminosity" or brightness. These steps minimize "peripheral light falloff" for even brightness across the frame even at wide apertures.

Tamron hesitates to reveal full details about proprietary technology, but the new 17-35mm Di zoom also benefits from a low dispersion glass element plus "highly balanced optical instrumentation to achieve high contrast in the low frequency range for higher resolution." The special types of glass also correct optical aberrations and distortion while optimizing color rendition, enhancing lens performance with any type of camera. Consequently, this ultra-wide angle Di zoom would be a suitable choice for serious photographers regardless of the type of equipment that they use.

Technical Specifications
Construction: 14 elements in 11 groups
Angle Of View (In 35mm Or Full Frame Format): 104Þ-63Þ
Maximum Aperture: f/2.8-4
Minimum Focus: 11.8" over entire zoom range
Maximum Magnification: 0.19x
Filter Size: 77mm
Dimensions: 3.3x3.4"
Weight: 14.4 oz
Available AF Mounts: Canon, Minolta, Nikon-D, Pentax
Street Price: $479