First Exposure: Sigma Telephoto Zoom Lenses

While the major camera manufacturers and most third-party lens manufacturers seem to be concentrating on introducing wide-angle and medium telephoto zoom lenses, Sigma Corporation is introducing long telephoto zooms. Two of these, both with 3.33X zoom ratios, are designed for digital SLRs while retaining compatibility with 35mm film cameras. They are the APO 120–400mm f/4.5–5.6 and the APO 150–500mm f/5.6–6.3. Both carry DG (designed for digital), OS (Optical Stabilizer) and HSM (Hyper-Sonic Motor) designations (more on these later). The lenses are available for Canon, Nikon, Pentax, Sigma and Sony cameras.

Other affordable lenses in these zoom ranges are virtually nonexistent and I know of no others in any price range that combine these focal lengths with a built-in optical stabilizer system. With the ability to handhold these lenses at three to four shutter speed settings lower than a non-stabilized lens, they should have wide appeal to sports and wildlife photographers who need long telephoto lenses but can’t be tied to a tripod. Even landscape photographers can benefit from the optical stabilizing system. Combined with a higher ISO setting, it can free them from carrying a tripod in their work.

Photographers will also benefit from the rear element focusing, which improves image quality by reducing aberrations over the focusing range, and the multicoating of strategic lens elements to reduce flare and ghosting. Both lenses also contain three SLD (Special Low Dispersion) glass elements to further improve image quality throughout the zoom range.

All of this technology, combined with the zoom range and solid construction, comes at the expense of length and weight. The 120–400mm is eight inches long at minimum size and weighs 3.87lbs.; the 150–500mm is 10 inches at its minimum size and weighs 4.2lbs. The length of both lenses increases considerably when they are zoomed to their maximum focal length.
This would make handholding at a reasonable ISO and shutter speed difficult if it weren’t for the built-in optical stabilizer (OS) system. With the OS turned on, I was able to consistently take sharp exposures at 1/125 second and a high percentage of sharp photos at 1/60 with either lens at its maximum focal length. And my testing was done with a Canon 40D, whose 1.6X multiplier meant maximum focal lengths of 640mm (for the 120–400mm) and 800mm (for the 150–500mm), respectively.

While this is impressive, it does take a few seconds for the image to stabilize with these lenses, particularly when first focusing on a distant subject. Subsequent focusing and stabilizing on the same subject is much quicker.

The OS system switch provides two positions, plus an off-mode. Mode 1 is used for most shooting situations. If you are tracking a subject moving horizontally, then Mode 2, which detects vertical shake only, is recommended. If the lens is mounted on a tripod, or if you are making a Bulb exposure, Sigma recommends turning the OS off.

Sigma makes other recommendations when using the lens. Because the OS draws power from the camera battery, it’s recommended that you turn off the system when it is not in use. I admit to never doing this and I never had a problem with battery drain on the 40D, even after hours of shooting. Sigma also recommends turning the OS off before attaching or removing the lens from the camera to prevent damage to the system. I rarely did this and I didn’t damage the lenses, but I always turn off a digital camera before making any configuration change, so this is what probably saved me. If you change lenses, batteries or cards with your camera turned on, make sure the OS on these lenses is switched to the off position before mounting or removing them.

There are two other switches on both lenses. One, just above the OS system switch, allows you to select manual focus or autofocus. Sigma’s Hyper-Sonic Motor (HSM) is quiet enough when autofocusing, but not as fast as I would have liked, especially when covering a large change in distance. With smaller distance changes, focusing and stabilizing were generally ready at the same time, but, with the action subjects for which these lenses would be used, I often wanted to press the shutter release all the way down before the autofocus and OS were ready.

Even with the lens in autofocus mode, it is possible to manually focus by rotating the focusing ring. However, if you have left the removable tripod collar on the lens, it is tough to make anything but minor focus adjustments. The focusing ring is relatively narrow and sits above the base of the tripod collar, leaving very little space for your hand. Fortunately, the zoom ring is located forward of the tripod collar and it can be easily turned throughout its range with the tripod collar attached.

The other switch on the lenses lies forward of the focusing ring. It is a zoom-lock switch with an on and off position. I found it useful when carrying the camera and lens around on a shoulder strap. With the switch on, it locks the zoom at its minimum focal length, preventing it from extending when the lens is pointed down—a thoughtful and useful addition. The lens must be set to its minimum focal length before turning the switch on, and the switch must be turned off before taking pictures.

In practical use, both of these lenses exceeded my expectations, physically and optically. Because both lenses far outweighed the 1.5-pound 40D, I expected the combination to be poorly balanced and difficult to handhold. However, it was not as much of a problem as I anticipated. A heavier camera body certainly would have improved balance, but at the expense of carrying more weight overall. With any camera body, you’ll be working your arm muscles handholding these, or any comparable lenses, for a day.

Sigma produces some highly regarded zoom lenses in its EX series, such as the 70–200mm f/2.8 and 120–300mm f/2.8 optics. However, neither of the lenses under consideration are EX lenses, so I was pleasantly surprised at their optical quality. While neither one will deliver the performance of an EX-series lens, or a top-of-the line lens from any of the camera body manufacturers with which these lenses are compatible, you will likely need to spend 2–3 times the price of these lenses to improve your image quality by approximately 20–25%.

Even shooting nearly wide open at its minimum focusing distance, the 120–400mm delivered very good sharpness and contrast. With a minimum focusing distance of five feet throughout its zoom range, the 120–400mm at 400mm delivers a magnification ratio of 1:4.2—something similiar to having a close-up lens attached to your camera. Quality improved further at smaller
apertures and greater distances.

The 150–500mm was at its best at the middle of its aperture range throughout the zoom range. I did notice some vignetting in images made during a boat race that wasn’t present in images shot with the 120–400mm. Other than that, which is easily correctable in post processing, image quality was quite acceptable.

Though when it comes to fast-paced sports shooting there are certainly other lenses out there to choose from, for other purposes, you would need to be pretty picky not to be satisfied with the image quality of these lenses.

Included with both lenses are a lens shade, front and rear caps, a padded fabric lens case and a shoulder strap that can be attached either directly to the lens or to the lens case. The APO 120–400mm f/4.5–5.6 is available for a street price of about $850. Street price of the APO 150–500mm f/5.6–6.3 is about $980. More information is available on the Sigma Corporation website at www.sigmaphoto.com.

Stan Sholik is a contributing writer for NewsWatch Feature Service. He is also a commercial photographer with over 30 years of large format studio and location experience.