At or near the 300mm focal length, the extra SLD elements in the higher priced APO version of the Sigma zoom offer advantages. Especially at f/5.6 and at f/8, image sharpness/contrast/resolution are higher. Out of focus areas (caused by shallow depth of field) should not be interpreted as a sign of poor resolution. (At 300mm; f/8; fill flash; B+W 81B filter; Ektachrome E100VS.)

Physical Characteristics. Incorporating the most frequently used telephoto focal lengths, the versatile Sigma 70-300mm zooms are compact and lightweight. The lens mount is made of stainless steel. Nearly identical (except for a gold stripe on the APO model) the barrels boast the ZEN matte finish which resists scratches.

While testing I noted the following:

• The rotary zoom and focus rings are wide and rubberized for a sure grip. A mere 45° rotation extends focal length from 70mm to 300mm. The zoom mechanism operates smoothly, especially in the APO model; the DL model is a bit stiff in the 200-300mm range but not unduly so.

• Like most of their competitors, the Sigma lens’ barrel length increases at longer focal lengths, to 6.7” at 300mm (APO model) and to 7.6” (DL model). The 1” wide rubber focusing ring is well placed so its movement is not impeded by your hand. Because it must rotate during AF operation, the mechanism is not very well damped, but there is a full series of legible distance markings in feet and meters.

• When the Focus Limiter switch is flipped from Normal to Macro--only possible at 300mm--both lenses are capable of extreme close focusing: to 37.4” for maximum magnification of 0.5x or 1/2 life size on the film frame. As of this writing, no other zoom lens of this type offers such high magnification. Many true “macro” lenses are limited to 0.5x magnification, too, unless accessories are used. In Macro mode, the zoom ring is locked at 300mm, but autofocus remains available; as Sigma recommends however, focus manually for critically precise control.

• Maximum reproduction ratio in Macro mode is 1:2. Four reproduction ratios are marked on the internal barrel--1:3.5, 1:3, 1:2.5, and 1:2--for those who need to know the exact level. The barrel protrudes an extra inch at maximum extension. Does the lens now become rather “front heavy”? Not at all, since the internal barrel is light in weight.

• Both lenses feature a diaphragm mechanism with nine blades, not eight as with their predecessors. This change does not sound too meaningful but it is worth noting. With a higher number of blades, out of focus highlights in the background of an image are rended close to circular instead of octagonal at every aperture. The effect is definitely more pleasing.

While a “fast” zoom lens like the Sigma AF 70-200mm f/2.8 APO EX HSM has advantages in low-light and action photography, an f/4-5.6 tele-zoom is fine for many outdoor situations such as this photo of the exterior of the George Eastman House. (DL Macro zoom; at 70mm; f/13; Ektachrome E100VS.)

APO Macro Super Optics. Because it includes three elements of Special Low Dispersion (SLD) glass--instead of two, as in the older APO version--the 70-300mm f/4-5.6 APO Macro Super zoom is very well corrected for chromatic aberration. High image sharpness, contrast, and clarity--plus freedom from color fringing even at the widest apertures--is obvious when the slides are viewed under a 10x loupe. This holds true in extreme close focusing, too, although the very finest image quality is then provided at two to three stops down from the maximum aperture.

DL Macro Super Optics. The more affordable DL version incorporates a single element of SLD glass to compensate for “extreme chromatic aberration.” Hence, it is not awarded the APO (“Apochromatic”) designation. The difference in optics is not obvious in 8x10” enlargements, a size that many people consider to be a “large print.” However, it is visible when slides are viewed under high magnification. In the 250-300mm range, it’s well worth stopping down to f/8 in order to get sharper images and to f/11 for high sharpness at the edges of the frame, too.

Evaluation. While shooting with the new zooms--and after examining my 25 rolls of Ektachrome E100VS slides--I made the following notes. Unless specified, they all relate to both Sigma models.

• Flare is well controlled. The long, bayonet-type lens hood (removable for reversed storage) is very effective, especially at focal lengths up to 200mm.

• Both lenses operated perfectly with an EOS-1N. Autofocus speed was quite good, capable of tracking vehicles traveling along a freeway. AF sound level is comparable to that of many other independent brand (and some camera makers’) lenses.

• The front element rotates when focusing (though not when zooming), as is common with affordable zooms; adjust polarizers and special effects filters just before tripping the shutter.

• The standard close focusing distance of roughly 5’ (1:4.1 reproduction ratio) was plenty for most subjects, reducing the need to switch over to the Macro mode.

• The Macro mode is definitely useful, making these zooms a suitable backup to a true 200mm macro lens. The longer 300mm focal length required in the extreme close focusing range is not a problem. The narrow angle of view allowed me to exclude background clutter, framing a nature subject against a small patch of greenery for example. Granted, the “Macro” feature would have been even more useful at all focal lengths. Still, this capability will definitely entice the nature photographer--and anyone who finds that most tele-zoom lenses do not focus adequately close.

• Slight pincushion distortion (bowing inward of lines near the edges of the frame) was observed, especially at longer focal lengths.

• In very close focusing, peak optical performance was provided at f/11 to f/16 with both lenses. These are the apertures I typically use for adequate depth of field. Slides made with the DL zoom are suitable for very sharp 5x7 prints or a half page reproduction in a magazine while those made with the APO zoom would make for fine 8x12 prints or full page magazine reproductions.

• At more typical focusing distances, the DL zoom proved to be a competent performer. Sharpness/ contrast/clarity and definition of intricate detail was high from 100-200mm, especially at f/8 and f/11 where the slides are impressive. Even at f/5.6, the DL lens is capable of image quality suitable for an 8x10 print in this focal length range. At the longer focal lengths, central sharpness was quite high but edge sharpness did benefit from stopping down to f/11.

• With the APO zoom, I found I could shoot at f/5.6 in the 70-200mm range and at f/8 at 200-300mm with edge to edge sharpness.

The DL Macro zoom provided accurate color rendition, without any apparent color bias. Particularly at certain focal lengths and apertures, sharpness, clarity, and definition of detail were impressive. (At 300mm; f/11 at 1/200 sec; monopod; Ektachrome E100VS at EI 200.)

Conclusion. The difference in image quality between the DL and the APO zoom was most noticeable at long focal lengths. With the DL zoom, I would recommend using an ISO 200 or 400 film, when shooting handheld. This will allow for apertures such as f/11 with adequate shutter speeds to prevent blur from camera shake. With the APO zoom, an ISO 100 or 200 film is usually adequate since there is no need to stop down beyond f/8 for optimum image quality. Many of the slides produced by the APO zoom met professional standards.

Both of these Sigma lenses fall into the affordable category, although the APO zoom costs roughly 30 percent more than the bargain-priced DL model. If you routinely order oversized enlargements, the extra cost of the AF 70-300mm f/4-5.6 APO Macro Super zoom will be a suitable investment. But for an entry-level zoom lens with impressive close focusing ability, the Sigma AF 70-300mm f/4-5.6 DL Macro Super offers excellent value for the price.

Photographers who have yet to visit the George Eastman House should definitely make plans to do so. The numerous exhibits and images chronicle the history of photography and make for an enjoyable and informative full day tour. The area also offers many photo opportunities, as well as all the amenities that photographers and their families expect. For additional information, contact the Greater Rochester Visitors Associa-tion, 126 Andrews St., Rochester, NY 14604; (800) 677-7282; fax: (716) 232-4822; www.visitrochester.com.

For more information on the Sigma lenses contact Sigma Corporation of America, 15 Fleetwood Ct., Ronkonkoma, NY 11779; (516) 585-1144; fax: (516) 585-1895; www.sigmaphoto.com.

Technical Specifications

Construction: 14 elements in 10 groups
Angle Of View (Diagonal): 34 to 8°
Min. Aperture: f/22 to f/32
Min. Focusing Distance: 59.1” and 37.4” in “Macro” mode
Max. Reproduction Ratio: 1:4.1 and 1:2 in “Macro” mode at 300mm
Dimensions: 2.9x4.7” (74.5x119mm); 58mm filter size
Accessories: Lens hood (both) and soft-sided carrying case (APO model only) included
Weight: 20.6 oz. (585g)
Mounts: AF: Sigma, Minolta, Nikon D, Pentax, and Canon