Article & Images by Peter K. Burian
Photographers shooting with full-frame DSLRs generally use a focal length of 24mm for wide angle photos but significantly shorter ultra wide lenses are also available. Granted some are fisheyes, great for special effects but not for more conventional image-making. The new Tamron 15-30mm lens is a true rectilinear lens however, well corrected for linear distortion, and its 110° field of view at 15mm actually qualifies it as a super wide. More importantly perhaps, it's equipped with premium-grade optical elements for excellent image quality as I discovered during my tests.
Primary Features
Mechanically and cosmetically, this is clearly a pro-calibre product with rugged construction, wide rubberized/knurled zoom and focus rings, a distance scale, and a handsome matte black finish. Both of the mechanical rings are well damped, with plenty of friction for a familiar "feel." Because of the unusually wide, constant maximum aperture of f/2.8 it's certainly large and heavy but balances well with a full-frame DSLR. The great light transmission to the AF sensors via the wide f/2.8 maximum aperture at all focal lengths ensures fast, reliable autofocus in low light.
In order to reduce the risk of flare in side lighting there's a built-in lens hood. It's notched or "corner cut" to prevent intruding into the image area. Super wide lenses such as this one cannot accept front-mounted filters because of the protruding element. A lens cover is included, with an innovative design that slips right over the lens hood.
Tamron's latest Vibration Compensation stabilizer -- employing a lighter moving three coil mechanism, for reduced weight/size and greater effectiveness -- is included in the Nikon and Canon mount models. Since a tripod is not allowed in the architectural locations that I was documenting, the VC system -- and the wide f/2.8 aperture -- were beneficial. They allowed me to make blur free photos in dark locations without setting a very high ISO level that would have produced more obvious digital noise.
Taken at 15mm
Taken at 24mm
The fast/silent Ultrasonic Silent Drive AF System with high torque provides quick response in both still and video recording. A full-time mechanism allows for fine-tuning focus in AF mode, although I rarely found this necessary in super or ultra wide image making. The lens also features nine curved aperture blades for smooth background blur, a pleasing bokeh.
Optical Technology
As hinted earlier, the optical formula includes high tech elements: an XGM aspherical plus three pieces of Low Dispersion glass to minimize all types of aberrations. These are intended for high edge-to-edge sharpness and to minimize geometric distortion and linear distortion, as the bending of straight lines.
Since a super wide angle lens is susceptible to flare and ghost images of the diaphragm aperture (from stray light striking the front element), the engineers specified the use of eBAND and BBAR coatings. In conjunction with the hood, these effectively control both issues and also help render colours in a uniform manner. And as a bonus, the front element benefits from a fluorine coating that repels water droplets and greasy fingerprints from the large convex surface.
Optical Evaluation
While reviewing my hundreds of images, made with a 36 megapixel Nikon D800, I reached the following conclusions. At every aperture from f/4 to f8 (the "sweet spots"), this lens produced images suitable for excellent 16x24" prints with impressive definition of intricate detail. Particularly those made at shorter focal lengths are absolutely stunning. Even at f/2.8 and at small apertures, image quality is adequate for beautiful 13x19" glossies.
Taken at 15mm
Taken at 30mm
Light falloff (darkening at the corners) is visible in images made at f/2.8 in the 15-20mm range, especially. That was easy to minimize by stopping down to f/5.6 or a smaller aperture, or corrected later with image editing software. (For example, the included SILKYPIX Developer Studio for Tamron offers a feature for this purpose.)
As expected with a super wide lens, there is some barrel distortion -- curving of lines near the edges of the frame -- at the shortest focal lengths. This is not visible in landscape images and can be corrected with software in architectural photos. Of course, any very short focal length produces "exaggerated perspective" or "expanded spatial perspective". And, when we tilt the lens upward -- as I often did for creative effects -- the so-called "perspective distortion" becomes obvious. This is not caused by any optical flaw so it's easy to prevent by ensuring that the camera back is perfectly level.
Final Assessment
Aside from the ability to include a vast area of a beautiful structure in a single image, the shorter focal lengths allow for a more obvious expanded spatial perspective than a 24mm lens. In other words, it's possible to render nearby objects as unusually prominent, at an apparent size far beyond the norm. Meanwhile, anything at a greater distance is "pushed back," making a desert vista or a sweep of wildflowers seem more expansive for an interpretive depiction of the scene. Take advantage of this exaggerated near/far relationship by including subject matter in the immediate foreground and in the mid-ground and the background; that will help to produce a three-dimensional "feel" in a two-dimensional photograph.
If you want to expand your visual horizons, the SP 15-30mm f/2.8 Di VC USD zoom can open new doors to creativity with a full-frame DSLR. An extremely wide angle of view does require some experimentation for creating effective images, search for suitable subject matter and try unusual viewpoints. Some of your pictures will seem "weird" but others will be dynamic or dramatic. Although not inexpensive, this lens offers many useful features, including an impressive optical formula, that will reward the investment with professional-calibre image quality.
Freelance Stock photographer Peter Burian (www.peterkburian.com) is the author of several books including Mastering Digital Photography and Imaging as well as co-author of many guide books to enthusiast-level cameras.