Sigma AF APO Macro 180mm f3.5 EX IF

Peter K. Burian  |  Jun 1, 2001

The HSM model lens mated firmly with an EOS-1N and maintained all camera functions including evaluative metering, A-TTL flash, and the five point AF system. Autofocus response was highly reliable, very fast, and nearly silent. (A 540EZ Speedlite; System Balanced fill flash; at f/8; Provia 100F at EI 200.)
Photos © 2001, Peter K. Burian, All Rights Reserved

Although 50-105mm focal length macro lenses are by far the most popular, many advanced nature photographers prefer longer lenses. Consequently, many camera manufacturers make a premium grade 180mm or 200mm macro lens. Now Sigma offers one, too, the APO 180mm f/3.5 EX IF, a professional tool with several advantages over their previous AF 180mm f/5.6 model. These advantages include: more rugged construction, wider maximum aperture, full 1x magnification capability, internal focusing, plus two low dispersion glass elements. And there is another benefit available in Canon, Nikon, and Sigma mounts: a Hyper-sonic Focus Motor (HSM).

The models for Minolta and Pentax AF cameras do not incorporate a focus motor and are not HSM designated; the camera's drive motor is employed for autofocus. There are other differences, too, but all models of this 180mm macro lens share an identical and excellent optical formula, as I discovered with nature subjects and flat objects such as postage stamps.

Design Characteristics
As expected with an f/3.5 telephoto macro lens, this one is very large and quite heavy due to extensive use of metal in its construction. The aluminum alloy barrel is finished in matte black with a silver sparkle. A removable, rotating tripod mounting collar and a 3.7" long hood are included; the latter bayonets onto the lens backward for storage convenience. The rubberized focusing ring is very wide (2.4") and is ribbed for a secure grip.

In addition to the usual Auto-focus/Manual Focus switch, there's a Focus Limiting switch with two settings: one for 24" to infinity and the other for extreme close-ups, from 18" to 24". Both provide quicker focusing in their ranges. There is a full distance scale under glass but no depth of field scale; frankly, most serious photographers own a camera with depth of field preview control. The focused distance scale also includes a reproduction ratio scale from 1:10 to 1:1. The latter is useful when you want a specific level of magnification. For 0.5x, for instance, rotate the focusing ring until 1:2 is shown in the scale. Move the camera back and forth (in relation to the subject) until critical focus is achieved. In manual focusing, the ring requires approximately a 300° rotation from infinity to closest focusing. That's a lot of rotation if you need to shift from long to short focused distances, but this design is useful for fine focus control. Slight rotation adjusts focus in very small increments, ideal in any macro lens.

The ability to fine-tune manual focus--without shifting out or autofocus mode--is often useful for critical focus with the HSM lens. Here, I did so to ensure focus on the subject's eye, instead of his hat. (A 540 EZ Speedlite; f/5.6; Provia 100F at EI 200.)

HSM Vs. Conventional Models
As mentioned earlier, Sigma offers this macro lens with ultrasonic HSM focus motor in Canon, Nikon, and Sigma AF mounts. This motor provides instant starting and stopping response for maximum autofocus speed and virtually silent operation. During AF operation, the focus ring does not rotate, making autofocus faster. The point of focus can also be manually adjusted even if the lens is set for AF operation in the camera's Single Shot AF mode.

The HSM model lenses are compatible with all Canon EOS and Sigma SA cameras. With Nikon cameras, however, they are fully compatible only with the following bodies: F5, F4 and N90 series, N70 and Pronea S. With other Nikon cameras, only manual focus operation is possible because the cameras do not contain the necessary electronic interface for operation with an ultrasonic focus motor in the lens barrel.

Because the non-HSM model does not have an ultrasonic focus motor, the lenses in Minolta and Pentax AF mounts operate a bit differently. They do not allow for manual focus override while in the "AF" setting. Also, in autofocus operation, the [AF/MF] switch on both the lens and the camera should be set to "AF." If you fail to do so, the focus ring will rotate. Autofocus will then be slower and your hand may impede the ring's operation, possibly causing damage to the camera's drive motor.

If you want to extend the focal length with tele-converters, note the following. The HSM lenses can be used with Sigma's 1.4x EX tele-converter for a 252mm focal length with an effective maximum aperture of f/4.9. Autofocus is maintained but only to about 47"; if you try to focus to shorter distances, the system automatically switches to manual focus. The non-HSM lens in Minolta and Pentax AF mounts provide only manual focus even with the 1.4x EX tele-converter. And, the 2x EX tele-converter can be used with all models of this macro lens, providing a 360mm f/7 lens, but only with manual focus operation.

Whether focusing or moderately close as in bottom image (0.5x magnification) or extremely close as in the top (1x) an in-camera light meter compensates for loss of light due to extension. Exposures remain accurate at all focused distances. (Both at f/16; Photoflex reflector; mirror lockup; Manfrotto tripod.)

Advanced Optical Design
In addition to the characteristics already described, here are some other design features of the APO Macro 180mm f/3.5 EX IF and EX IF HSM lens. Focus can be varied from infinity to 18" for full 1:1 life-size reproduction, also called "1x magnification" and "life size." A subject that is 1x1.5" in size will fill a 35mm film frame. In more practical terms, a honeybee will be exactly bee-size on a negative or slide without enlargement. Supple-mentary close-up lenses or extension tubes are not required for a 1:1 reproduction ratio, so image sharpness is not degraded and there is no additional loss of light transmission.

The wide f/3.5 maximum aperture makes focusing on a bright viewing screen a pleasure in low-light conditions as in the woods in deep shade. The two SLD (Special Low Dispersion) glass elements--effectively control chromatic aberration and astigmatism, two common optical flaws. This helps to provide superior sharpness and color fidelity throughout the focusing range.

Focusing is internal, so the physical length of the lens does not change even in extreme close-up work. This is appreciated especially when working with a tripod: the center of gravity does not shift so balance remains uniform. The front element does not rotate, useful when using a polarizer because the filter's effect does not change while focusing.

At 1x magnification as in the top image, these stamps are rendered life size on the film frame. Many shorter macro lenses require an extension tube or "life-size adapter" to reach this level, providing only 0.5x magnification without an accessory as illustrated in the image bottom. (At f/8; Photoflex reflector; Manfrotto tripod; Velvia film.)

A "floating system" is employed for close distance aberration compensation. Part of the optical system moves or "floats" when focusing; the distance between certain elements is varied according to the shooting distance. Aside from controlling optical aberrations, there is virtually no shift in the point of focus when small apertures are set.

Take note that as with most macro lenses, there is some loss of light due to extension in extreme close focusing. The true f/number does change: by 1.1 stops at 0.5x magnification and by 1.4 stops at 1x magnification. In-camera TTL light metering systems compensate automatically; if you use an accessory light meter, you'll need to compensate manually. For the amount of compensation at any level of magnification, refer to the chart in the instruction sheet.

The Long Lens Advantage
Although shorter macro lenses are smaller, lighter, and less expensive, a 180mm focal length macro offers several advantages in outdoor photography. First, the narrower angle of view of the longer focal length encompasses a smaller area of a cluttered background. This makes it easier to isolate a tiny subject against a small patch of greenery for a more aesthetically pleasing effect. With a small, three-dimensional blossom or insect, perspective is also more pleasing with a 180mm vs. a 50mm focal length because you can shoot from a greater distance.

When you focus at 18" for maximum magnification, the distance from the front element to the subject is about 9". That's not a great deal of working distance, but far more than the 6" you'd get with a 100mm macro lens or the 3" you'd get with a 50mm model. Because you don't need to get excessively close to the subject, high-magnification nature photography becomes more practical. You'll be less likely to trample other flowers in a garden, scare off a skittish butterfly, or knock the dew off a spider's web. And, by shooting from farther away the camera equipment should not cast a shadow over the subject. That extra space will also allow you to position a multi-flash system and/or a reflector panel for supplementary lighting for better light control.

Lens Evaluation
As mentioned at the outset, the image quality produced by the Sigma APO Macro 180mm f/3.5 EX IF lens was impressive. Images made with extreme close focusing appear razor sharp under an 8x loupe, with the most intricate detail crisply defined. Contrast is snappy and there's no evidence of color fringing even at f/3.5. I found no need to stop down to f/16 for high sharpness across the entire frame as with some macro lenses. In fact, image quality is excellent at all f/stops from f/4 to f/8. At f/11 and f/16 overall sharpness remains very high. By f/22, center sharpness is still high, but corner sharpness does suffer, as with many lenses, due to diffraction, the bending of light rays as they enter a very small aperture. However, the greater depth of field produces an impression of higher sharpness, because all parts of a blossom are within the range of sharp focus. Hence, it's not necessary to avoid these apertures.

Although the lens is not lightweight, it's still manageable in handheld photography and nicely balanced with heavy SLR cameras. This is a fine all-purpose telephoto lens, especially with the EX 1.4x tele-converter. Autofocus with a Canon EOS-1N was very quick, smooth, highly reliable, and very fast in most cases. Manual focus operation is smooth and well damped, with just the right amount of friction for a familiar feel. However, when changing from close-ups to distant subjects, manual and autofocus are not as quick as with the Sigma APO 70-200mm f/2.8 EX HSM lens. That's because of the greater distance the focus system must travel.

Long macro lenses, such as this Sigma 180mm, provide great working distance in high-magnification work, making nature photography convenient. Image quality at 1x is high at all f/stops. (Above top image: f/3.5, above, bottom: f/8, below: f/16; Photoflex reflector; Manfrotto tripod; Velvia film.)

At the common 6' to infinity distances, image quality is excellent at all apertures from f/5.6 to f/16; this consistency is a sign of well-designed optics. At maximum aperture, central sharpness remains high, an important consideration in telephoto photography, where the primary subject is rarely near a corner of the frame.

Even in extreme sidelighting or when shooting directly into a light source, the effects of flare were minimal. This confirms the effectiveness of the lens hood and the internal precautions employed by the designers. Thanks to the nine aperture blades, out-of-focus highlights--such as the rising sun in the background--are rendered as round blobs at most apertures, a very pleasing effect. Macro lenses with fewer blades produce hexagonal highlights at all f/stops except the maximum aperture, giving this Sigma model an advantage over some of the others.

Final Assessment
No matter how extraordinary the optical potential of any macro lens, technical proficiency is a prerequisite for sharp images at high magnification. Even the most expensive optics will produce blurry pictures if you don't pay attention to technique. For the best results in close-up photography, consider these hints. Use a rigid tripod and head at all times, and trip the shutter with a cable release. If your camera has a reflex mirror pre-lock control, use it to raise the mirror in advance. This eliminates internal vibration from mirror-slap. If your subject is swaying in the breeze, wait until a lull in the wind or take steps to secure it to avoid motion blur.

In extreme close-ups, focus carefully. The zone of sharpness is extremely narrow, so do not count on depth of field to mask focusing errors. Try to set up the equipment so the film plane (camera back) is aligned parallel with an insect or tiny blossom. You may be able to render it all within the range of apparent sharpness even at full 1x magnification. Use the camera's "preview" or "stop down" button to check the effect at various f/stops.

Though not inexpensive, this Sigma APO Macro lens--with premium grade optics and the latest technology--offers good value. It's also mechanically solid and seems likely to provide long-term reliability. Used with the right shooting techniques, it will pay dividends in terms of superior image quality, especially in nature photography. Ideal in focal length and just about every other category, the APO Macro 180mm f/3.5 EX IF HSM is the most desirable macro lens ever built by Sigma. For additional specifics on the extensive series of Sigma lenses, contact a dealer, or Sigma Corporation at (631) 585- 1144, fax: (631) 585-1895, or visit their web site at www.sigmaphoto.com

Technical Specifications
Focal Length: 180mm
Maximum Aperture: f/3.5
Lens Construction: 13 elements in 10 groups (two SLD elements)
Angle Of View: 13.7°
Number Of Blades: Nine
Minimum Aperture: f/32
Minimum Focusing Distance: 18.1" (0.46m)
Maximum Magnification: 1x (1:1)
Filter Size: 72mm
Lens Hood: Bayonet type; included
Dimensions: 3.14x7.06" (80x179.5mm)
Weight: 39.5 oz (1120 g)
AF Mounts: HSM model: Canon, Nikon (D), Sigma; Non-HSM: Minolta, Pentax
MSRP:US $1534

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