A Fast Standard Zoom for digital SLRs

The Tamron AF 17-50mm f 2.8 XR Di II is a lens designed specifically for digital SLRs and their smaller image sized image sensors. It is a lens manufactured with Low Dispersion (LD) glass and its operation is based on Internal Focusing (IF). This means the front lens barrel does not rotate and makes using circular polarizers virtually effortless.

This is a lens that I was able to borrow from a member of an Air National Guard unit currently deployed to Iraq. He uses it on USAF owned Nikon digital cameras to include the now discontinued D1X and the current D2X. I have used it on both and based on my observations would consider using it on my Nikon D200 when I return home.

THE LENS:

This is a relatively lightweight lens for its size and focal length. It weighs in at just under a pound (15.3 ounces) and is a constant aperture lens with a speed throughout its zoom range of f2.8. Due to the nature of the crop factor in smaller sized digital sensors, this lens, which starts at 17 mm offers a wider field of view than a normal 18 or 19 mm wide angle lens. On Nikon digital camera bodies, this lens would be the equivalent of a 26-78 mm lens used on a 35 mm FILM SLR. However, since it is designed for digital, it cannot be used without vignetting on a film camera body.

This lens has a fast aperture of f2.8 that allows for a natural soft focus effect for backgrounds when the aperture is stopped down to f2.8

LENS CONSTRUCTION:

This lens is constructed with three elements of what Tamron refers to as "Extra Refractive Index" glass, two Hybrid Aspeherical lens elements and one element of Low Dispersion glass. Tamron claims that this combination of manufacturing and lens technology allows for high level image quality while benefiting from compactness of size. Each of the lens elements benefits from internal lens coatings to minimize or eliminate ghostings and flare.

The outer barrel construction is a hardy ridged rubber with a fairly broad zoom ring and a zoom lock to prevent lens creep when the camera is held downward. The focusing ring is somewhat more narrow, but still easy to grip and operate. Unlike its competition from Sigma, this Tamron lens, like so many found in the Tamron family, shows a considerably smoother action when the lens is manually focused. I found this trait to be welcome, but I feel that I should also point out that there did seem to be a tad more play than I would have liked and I think that after years of use, that the manual focus ring and action could end up with more slop than one might like.

Although this lens is not billed as a macro lens per se, it can be used as one in a pinch. Its minimum focus distance is 10.6 inches or 27 cm.

Below are some specifications that you might find helpful when considering this lens or others in the same class.

Focal length: 17-50 mm

Max. Aperture: f2.8

Min. Aperture: f32

Angle of View: Diagonal: 78 degrees 45 minutes - 31 degrees 11 minutes.

Horizontal: 68 degrees 37 minutes - 26 degrees 7 minutes.

Vertical: 49 degrees 1 minute - 17 degrees 22 minutes*

* This information provided by Tamron in their literature.

Lens Construction: 16 elements in 13 groups as I described above.

Minimum focusing distance: 10.6 inches or 27 cm (Metric)

Max. Magnification Ratio: 1:4.5 at 50 mm and Max. Focusing Distance.

Overall Lens Length: 3.2 inches or 81.7 mm

Max. Diameter: 2.9 inches or 74 mm.

Filter Size: 67 mm

Weight: 15.3 ounces or 434 grams

Number of blades in Lens Diaphragm: 7 (makes for a nice, soft out of focus image).

Accessories included with lens: A Petal shaped or flower lens hood.

Available lens mounts: Canon AF, Nikon AF-D and Konica-Minolta AF-D*

* With the sale of K-M's digital SLR product line to SONY and the latter's use of the K-M lens mount system, this lens 'should' work on the SONY dSLRs as they are introduced as well.


IN-USE OBSERVATIONS:

I have used this lens in only one type of climate and environment. My current location is arid, hot and dusty. The lens has worked well but I think its exterior construction, especially the AF and Zoom rings leave it prone to picking up and retaining a great deal of dust and grit. In a more temperate location and climate, that would not be a failing or worth mentioning. The fairly wide mouthed outer barrel DEMANDS that the lens be covered with at the bare minimum, a UV or Daylight filter. At 67 mm, the filter size will mean that while not cheap, they will not be the most expensive, either.

I found most of the images I obtained through the lens to be quite sharp and while Tamron stipulates that this lens can be used for macro work, I did not find it to be a "best in class" performer in that category. I noticed some softness at 50 mm when I tried to use the lens for close-ups. For really critical close up work, I would recommend a lens that has been specifically designed for that purpose, rather than a digital zoom that would at best be a compromise.

Given that this lens is digital specific, it functions well when one compares it to an equivalent film body lens at 26-78 mm. I own a Sigma 28-70 f2.8 that I use on both Nikon film and digital bodies and this Tamron lens fits in quite nicely at the wider end of the spectrum since the 28-70 lens is further magnified to 43-105 in digital format. That is the problem with dSLRs and their smaller sensors: the crop factor and if one continues to utilize lenses designed when film was still king, then buying a lens of this type almost becomes a necessity for wide-angle photography.

For the most part, I have enjoyed using this lens and will give consideration to buying one (or a competing equivalent) when I return home. It delivers faithful and contrasty imagery for a moderate price with a fast maximum aperture.

If you use a Canon, Nikon or K-M dSLR, take a look at this lens. It could save you money and deliver near to OEM type quality.