By Joe Farace
Tamron offers two series of lenses specifically aimed at digital SLRs shooters. Digitally integrated design (Di) lenses are intended for use with digital SLRs while Di-II lenses, such as the AF18-250mm f/3.5-6.3 lens I tested, are expressly designed for SLRs with 24x16mm image sensors and maximized for smaller-sized imaging chips. That imager size, often called APS-C, is actually a little smaller than an APS-C film frame and much smaller than a 35mm film frame. The lens is available in Konica Minolta AF-D (a.k.a. SONY), Nikon AF-D, Pentax AF, and Canon EF mounts. (See “EF vs. EF-S Mount.”)
The AF18-250mm f/3.5-6.3 lens is compact, especially for one that has a zoom ratio of 13.9X, and features a black coating over the entire lens barrel and a gold-colored band between the focus and zoom rings letting you know it’s a Di-II lens. The rubber patterns on the focus and zoom rings are not only attractive but provide a solid gripping surface for quick handling in fast moving situations like travel and wedding photography.
Caption: To show the versatile focal length range of Tamron’s SP AF18-250mm f/3.5-6.3 Di-II lens, I attached it to a Canon EOS 30D mounted on a Flashpoint carbon fiber tripod. These two photographs were made in the same spot in Denver’s Forney Museum of Transportation. At 18mm (top) the lens shows various classic cars with a 1934 Pierce-Arrow Limousine in the foreground. With the lens at 250mm (above), I can make a close-up of the details of the Pierce-Arrow’s radiator mascot, an archer. ©2007 Joe Farace (click/right-click to download 18mm full-size image, 250mm full-size image 23.5MB each)
To minimize on-axis chromatic aberration at the 250mm, the lens’ optical design incorporates an LD (Low Dispersion) glass element and an AD (Anomalous Dispersion) lens in its first group. Two hybrid aspherical lens elements permit a smaller lens diameter, allowing it to use affordable 62mm filters while maintaining the same maximum apertures as similar lenses. An internal focusing system suppresses focusing aberrations and improves optical performance by minimizing light loss in the corners. That also means that modular filter users don’t have to worry about a rotating front element. My favorite feature of the AF18-250mm f/3.5-6.3 is the short minimum focus distance (17.7 inches) it maintains throughout the entire zoom range. At 250mm, this results in a magnification ratio of 1:3.5. It may not be true macro, but this capability provides a great way to make close-ups when you’re not close up.
Caption: The SP AF18-250mm f/3.5-6.3 Di-II I lens is useful for travel and landscape photography such this 22mm focal length photograph of Clear Creek, made on a sunny but chilly Colorado day. Exposure was 1/400 second at f/11 in Aperture Priority mode, ISO 200. ©2007 Joe Farace (click/right-click here to download full-size image, 23.5MB)
Real World Testing
I didn’t use the AF18-250mm f/3.5-6.3 to photograph any lens resolution charts, and I don’t expect you will either. Instead, I attached the lens to two different Canon EOS digital SLRs and captured images made under many kinds of lighting and environmental conditions. Even under cold winter conditions, I never encountered any kind of mechanical or optical flaw in the lens that prevented me from capturing the image I wanted. I used the lens to photograph indoors and outside; image sharpness was more than acceptable at all focal lengths, and it never felt like I needed anything more.
Caption: This locomotive was photographed at an indoor museum using the AF18-250mm f/3.5-6.3 attached to a tripod-mounted Canon EOS 30D. Exposure was 1/2 second at f/11 in Aperture Priority mode, ISO 1600. Yup, it was that dark, and I even added a 2/3-stop exposure compensation to make sure the shadows didn't hide that fire truck in the background. ©2007 Joe Farace (click/right-click here to download full-size image, 23.5MB)
Because of the AF18-250mm f/3.5-6.3 lens’ internal focus mechanism, manual focusing with the lens was fast and crisp, but I rarely used it that way because the autofocus with both EOS bodies was fast and crisp. The build quality of the lens is just a touch better than you might expect for its price point and its compact size makes you want to keep it on your camera all day. When testing its predecessor, the AF18-200mm f/3.5-6.3 XR Di II lens, I was able to capture dramatic drag racing images even from the grandstands. Because racing season is months away, I was only able to photograph static rather than racing cars with this improved lens, but I’m guessing that with the extra 50mm of focal length, the AF18-250mm f/3.5-6.3 will be an even better lens for photographing sports action.
Caption: The versatile focal length range makes the SP AF18-250mm f/3.5-6.3 Di-II lens wonderfully useful for capturing candid moments, whether it’s a bride with her father or a dad with his daughter playfully throwing rocks into Clear Creek. This photograph was made at the 155mm focal length to get the cropping that I wanted, showing enough of the background to tell a story. Exposure was 1/250 second at f/11 in Aperture Priority mode, ISO 200. ©2007 Joe Farace (click/right-click here to download full-size image, 23.5MB)
The AF18-250mm f/3.5-6.3 has a zoom lock that prevents “unwanted barrel extension” when carrying it mounted on your camera. TIP: Use it. There were many times when I was shooting at the 18mm focal length and flipped the camera over to view the image on LCD only to discover that when I flipped the camera back over, it had zoomed out to a longer focal length. The lock only works at the 18mm setting and any lack of stickiness probably contributed to the speed that the AF18-250mm f/3.5-6.3 Di-II zooms and focuses.
A tulip-shaped lens hood is included with the lens as a standard accessory. TIP 2: Use it. The flare-reducing hood produces optimum shading from light outside the image field and entering the frame. The use of coatings on the cemented surfaces of some lens elements and multiple-layer coating on others, keep ghosting and flare to a minimum. Flare is well controlled with the AF18-250mm f/3.5-6.3. I had to deliberately point the lens at the sun to see any flare, and even then it was modest considering these kinds of extreme conditions.
Caption: I often like to point my lens at the sun and use small apertures to get starburst effects like the one in this bridge photograph (1/200 second at f/22 in Aperture Priority mode, ISO 200). Because of the optical lens and hood design of the AF18-250mm f/3.5-6.3, flare is so well controlled that you have to deliberately point the lens at the sun to see any and that is modest considering the extreme way this image was captured. ©2007 Joe Farace (right-click here to download full-size image, 23.5MB)
Tamron’s AF18-250mm f/3.5-6.3 lens is a well constructed zoom lens that delivers tremendous value with its versatile focal length range and optical and mechanical performance that exceed what you might otherwise expect based on its modest price.
The AF18-250mm f/3.5-6.3 Di-II LD Aspherical (IF) Macro lens is designed exclusively for digital SLRs with APS-C sized imager sensors and is not recommended for use with cameras with image sensors larger than 24x16mm or 35mm film. The version I tested was in Canon EOS mount but is not an EF-S (Electro-Focus Short Back Focus) lens so it attaches to more EOS digital SLRs than Canon’s own proprietary mount. EF-S lenses have a rubber ring surrounding a rear element that fits deeper inside the camera than an EF lens and will hit the mirror if you try to mount an EF-S lens on non-compatible SLRs. EF-S lenses only fit the EOS Digital Rebel, Rebel Xt, Rebel Xti, 20D and 30D. Tamron’s Di-II lenses will attach to all of these different Canon models plus the EOS D30, D60, and 10D.
Caption: Unlike some of Canon’s wide-angle EF-S lenses, the Tamron AF18-250mm f/3.5-6.3 is compatible with older Canon EOS digital SLRS such as the 60D used to capture this image. This particular 60D was converted (www.irdigital.net) to direct infrared capture that worked well considering the unpredictable nature of non-deciduous foliage and snow. Captured as a RAW file, the exposure was 1/180 second at f/8 at the 42mm focal length. ©2007 Joe Farace (click/right-click here to download full-size image, 18MB)
SPECS: Tamron SP AF18-250mm f/3.5-6.3 Di-II LD Aspherical [IF] Macro
Focal Length range: 18-250mm
Maximum Aperture: f/3.5-6.3
Minimum Aperture: f/22
Angle of View: 75°33’ – 6°23’ (with APS-C sensor size or equivalent)
Lens Construction: 16 elements/13 groups
Minimum Focus Distance: 17.7-inches over entire zoom range
Diaphragm Blades: 7
Filter Size: 62mm
Max. Magnification Ratio: 1:3.5
Flower-Shaped Lens Hood: Standard Accessory:
Compatible Mounts: Canon AF, Sony/Maxxum AF-D, Nikon AF-D and Pentax/Samsung AF
Size: 2.9 x 3.3 inches
Weight: 15.2 oz
*Specifications based on Nikon mount