Many thanks to Gene (FM Forum: gasrocks) for providing the lens for testing

Introduction

Sigma APO MACRO 150mm f/2.8 EX DG HSM is one of five dedicated macro lenses that the company currently offers in its lineup. The lens is available in Canon, Nikon, Sigma and Four Thirds mounts. Priced at ~US$550 (as of March 2008), the lens is positioned to compete for the dollars of both amateur, prosumer and professional photographers alike.

The optical construction of the lens consists of 16 elements in 12 groups, including two SLD (Super Low Dispersion) glass elements designed to reduce amounts of various color aberrations. The lens features a floating focusing system that helps reduce astigmatism and spherical aberration. The build quality of the lens is superb - like all EX marked Sigma lenses, this one sports a hardened plastic barrel with crinkle finish. There is no wobbling inside or out and the lens looks and feels sturdy. Focus ring is pretty smooth, however, like most modern Sigma auto-focus lenses, Sigma APO MACRO 150mm f/2.8 EX DG HSM does not have a dedicated aperture ring, so all aperture settings have to be set directly from the camera.

The lens is about average is size and weight when compared to other telephoto lenses, measuring 79 x 137mm (3.1 x 5.4in) and weighing 895g (31.6oz). The lens sports a true inner focusing mechanism so the length of the lens stays constant at all times. Speaking of the focusing - Sigma incorporated an HSM type AF along with a fully manual focusing system (you can switch between the two modes using an AF/MF switch on the side of the barrel). To aid in focusing, Sigma also incorporated a 3-mode focusing distance limiter, which allows you to restrict the focusing distance between 38cm (the minimum focusing distance of the lens) and 52cm, 52cm and infinity, and 38cm and the infinity. The first mode is obviously going to be helpful during macro work, while the second is more suitable for regular telephoto photography. At its minimum focusing distance the lens will give you a 1:1 life-size macro. The minimum supported aperture is f/22 and the lens accepts 72mm screw-in type filters.

Image

The factory box includes Sigma APO Macro 150mm f/2.8 EX DG HSM lens, front/rear caps, vinyl case, LH780-3 lens hood, tripod collar, manual and registration card. The lens is compatible with Sigma's 1.4x and 2x APO Tele-Converters, which turn the lens into a 210mm f/4 AF and 300mm f/5.6 MF tele-macro lens respectively. Since the lens was designed to fit traditional 35mm camera system, when used on an APS-C type camera with 1.6x crop factor, the field of view of the lens will be equivalent to that of a 240mm lens on a full frame camera.

 

Summary
Lens Composition 16 elements in 12 groups
Angular Field ~16 degrees
Minimum Focus 38cm/15in
Focusing Action AF/MF, HSM
f-stop Scale f/2.8-f/22, electronic
Filter Size 72mm
Lens Hood LH780-3 (included)
Weight 895g/31.6oz
Dimensions 79.6x137mm/3.1x5.4"
Lens Case Vinyl (included)

 

Field Tests

Sigma APO Macro 150mm f/2.8 EX DG HSM is a pretty popular lens among photographers, thanks to its aggressive pricing vis a vis its main rivals from Canon and Nikon, as well as superior build quality and the (supposedly) improved performance characteristics attributed to the use of special low dispersion glass elements. The lens handles like any other medium telephoto lenses out there, so there's no major difference worth mentioning here. However, the build quality and the fact that Sigma threw in a lens shade and a tripod collar definitely help differentiate the lens, at least initially. Speaking of the tripod collar - you should not have any problems shooting hand-held, since the lens is not that heavy, but when you decide to mount the camera on the tripod, you'd better attach fasten the mount to the lens collar rather then the camera to achieve better balance. This is going to be especially important for lighter cameras like Digital Rebel series since the lens can tip a lightweight camera.

The lens handled quite well in the field. The AF system of the lens is reasonably fast and accurate - there's a typical in/out of focus movement at macro distances, but that can easily be minimized by switching the focusing limiter to 0.38-0.52 position. And besides, if you're shooting macro, you are more then likely to focus the lens manually. The focusing ring rotates for ~270 degrees when going from the infinity to the macro distance, with longer spacing allocated at the closeup distances (~180 degrees of rotation between 0.38m and 0.7m), which obviously would be helpful for precise focusing.

Resolution-wise, the lens showed pretty consistent performance - images looked adequately sharp across the picture frame and throughout the tested aperture range. There did not seem to be any noticeable difference in image quality between APS-C and FF cameras, except at f/2.8, where FF images looked slightly softer around borders. But then again, the difference was pretty negligible and is unlikely to affect the real-life photography.

 

ISO 400, 1/60, f/2.8, 150mm (Canon 5D)
ISO 400, 1/60, f/2.8, 150mm (Canon 5D)

 

When shot with wide open aperture, the lens produced mostly oval shaped out-of-focus highlights - this is rather unusual in photographic lenses, since this characteristic is more common to anamorphic lenses that expand horizontal or vertical aspect of the scene. Moreover, the OOF highlights sometimes showed harsh edge outlining, which hints on slight over-correction in spherical aberration. The good news is that the lens showed mostly neutral and eye pleasing contrast transitions in OOF areas (take a look at the picture of the yellow flower in the image gallery for example) with no major sign of double edging around OOF objects.

 

ISO 400, 1/15, f/2.8, 150mm (1:1 macro, Canon 5D)
ISO 400, 1/15, f/2.8, 150mm (1:1 macro, Canon 5D)

 

One of the more interesting aspects of this lens is obviously its life-size macro capabilities. In theory, the long(er) focal length of the lens should benefit those who try to shoot closeups in situations where getting too close to a subject is impossible. However, the minimum focusing distance offered by the lens is not that much 'father' then the minimum focusing distance of many shorter macro lenses - compare, for example, the minimum focusing distance of 0.38m for Sigma's 150mm macro and 0.31m for Canon's 100mm macro or 0.32m for Sigma's 105mm macro. Those of you who do really need to get pretty 'far away' from the subject will probably be better off with a 180mm macro (but don't forget the crop factor if you're using the lens on an APS-C type body - 150mm turns into 240mm on Digital Rebel XTi).

Image quality at macro distances remained pretty good throughout the aperture range - there does not seem to be any visible drop-off in quality, although it's obviously hard to eyeball border image quality here due to the shallower depth of field.

 

Vignetting @ f/2.8 - full frame vs 1.6x crop (150mm)
Vignetting @ f/2.8 - full frame vs 1.6x crop (150mm)

The lens produced quite noticeable vignetting on a full frame Canon 5D with wide open aperture. This is somewhat disappointing, given that we are dealing with a moderately fast telephoto prime here. The good news is that vignetting is reduced with stopped down aperture and Sigma APO Macro 150mm f/2.8 EX DG HSM is no exception - vignetting is pretty much gone by f/5.6. Better news yet, vignetting is pretty much non-existent on an APS-C camera throughout the aperture range.

Vignetting on a full frame camera is not the only issue users should be concerned about. The lens fell prone to occasional, but pretty nasty flare with direct strong light source located near or within the picture frame. The shots below demonstrate probably the worst case of the flare that the lens exhibited. The sun was hitting the lens at ~65 degrees. At wider apertures the flare  manifests itself through a greatly reduced contrast across the entire picture frame (which is common for majority of lenses by the way) and the typical rainbowish flare (at the bottom of the picture on the left), while at smaller apertures the lens also fell prone to quite pronounced ghosting. All-in-all, using a lens hood or recomposing the shot to avoid the majority of stray light is highly recommended.

 

Left: ISO 100, 1/800, f/2.8 Right: ISO 100, 1/150, f/8 (Canon 5D)
Left: ISO 100, 1/800, f/2.8 Right: ISO 100, 1/150, f/8 (Canon 5D)

 

Aside from the flare and vignetting problems described above, Sigma APO Macro 150mm f/2.8 EX DG HSM showed decent handling of color - color reproduction was more or less accurate, albeit the color palette seemed a little bit warm to the eye. Color fringing seemed to be under control, with no signs of lateral or longitudinal aberration. There also was no sign of distortion, which is not surprising for a telephoto lens.

 

ISO 100, 1/1250, f/2.8, 150mm (100% crop)
ISO 100, 1/1250, f/2.8, 150mm (100% crop)

 

Lab Tests

Please note that MTF50 results for APS-C and Full-Frame cameras as well as cameras from different manufacturers are not cross-comparable despite the same normalized [0:1] range used to report results for all types of cameras.

 

Canon APS-C: Sigma APO Macro 150mm f/2.8 EX DG HSM showcased excellent performance on an APS-C type Canon 400D. The lens produced pretty balanced overall results across the tested aperture range, with both center as well as borders remaining on very solid levels from f/2.8 through f/8. Quality starts to degrade slightly around f/11 - a typical effect of diffraction, and will likely degrade even further at smaller apertures. Still, the lens is capable of producing excellent 16in prints in the f/2.8-f/8 aperture range and very decent 24in prints in the f/4-f/8 range. Conclusion? Resolution-wise, overall results can be considered quite solid - this is what you would expect from a good lens, macro or telephoto.

 

MTF50 (Line Width/Inch on the Print) @ 150mm
MTF50 (Line Width/Inch on the Print) @ 150mm

 

Normalized raw MTF50 @ 150mm
Normalized raw MTF50 @ 150mm

 

CA on the APS-C camera should not be a major problem for most users. The lens produced minimal traces of CA in the center, generally no exceeding ~0.3px throughout all tested aperture settings. CA around borders was slightly higher, reaching ~0.8px at the widest aperture and then slowly dropping to ~0.6px around f/11.

 

Chromatic Aberration (APS-C) @ 150mm
Chromatic Aberration (APS-C) @ 150mm

 

Here are 100% crops, taken with an APS-C type Canon Digital Rebel XTi, comparing image borders at f/2.8 and f/8.

 

Image borders @ 150mm (100% crop): f/2.8 vs f/8
Image borders @ 150mm (100% crop): f/2.8 vs f/8

 

Canon FF: The lens gave up a little ground in performance when used on a FF camera. Center performance still remained quite solid at f/2.8 and only improved with stopped down apertures. In the f/4-f/11 range, center image quality was simply outstanding. On the other hand, border quality at f/2.8 is where the weakness was most noticeable - quality here is OK, but certainly not breath-taking. The good news is that border quality improved quite nicely once the lens is stopped down to f/4 and remained on the consistently high level all the way through f/11. Conclusion? Very few lenses show consistently high performance throughout all aperture levels - most actually have some weakness at wider apertures. Sigma APO Macro 150mm f/2.8 EX DG HSM is no exception here and as such can be considered a solid overall performer, but not necessarily 'the king of the hill'.

 

Normalized raw MTF50 @ 150mm
Normalized raw MTF50 @ 150mm

 

The lens showed very minimal amount of barrel distortion - at ~0.09%, distortion should not even register in any of your shots.

 

Distortion (FF) @ 150mm
Distortion (FF) @ 150mm

 

Chromatic aberration on a FF camera was under control. CA in the center never exceeded ~0.3px, while CA around borders averaged ~0.55px throughout the tested aperture range, with the maximum level of ~0.65px registering at f/2.8.

 

Chromatic Aberration (FF) @ 150mm
Chromatic Aberration (FF) @ 150mm

 

Here are 100% crops, taken with an FF type Canon 5D, comparing image borders at f/2.8 and f/8.

 

Image borders @ 150mm (100% crop): f/2.8 vs f/8
Image borders @ 150mm (100% crop): f/2.8 vs f/8

 

Alternatives

Assuming you're looking for a macro lens, then you're in luck! Sigma alone makes four other dedicated macro lenses capable of producing 1:1 life-size magnification. These are Macro 50mm f/2.8 EX DG, Macro 70mm f/2.8 EX DG, Macro 105mm f/2.8 EX DG and APO Macro 180mm f/3.5 EX DG IF HSM. If you're using a Canon SLR, then you might also want to take a look at Canon's two excellent macro lenses EF 100mm f/2.8 Macro USM and EF 180mm f/3.5L Macro USM. Canon's other excellent macro lens, EF-S 60mm f/2.8 Macro USM could also be a good choice assuming you work with an APS-C type camera. Finally, you might also consider Tokina's AT-X M100 AF PRO D 100mm f/2.8 Macro (which is also suitable for APS-C type cameras only) and Tamron's SP AF 90mm f/2.8 Di Macro and SP AF 180mm f/3.5 Di LD Macro. Most macro lenses are pretty solid performers, so you would need to decide what focal range suits your needs and start from that point. You might also want to check out the side by side comparison of macro lenses, found in the Macro Challenge section.

 

Recommendation

Sigma APO Macro 150mm f/2.8 EX DG HSM is a very solid performer - the lens shows excellent image quality combined with practically non-existent distortion and low levels of color fringing, excellent build quality and very reasonable street price. There are a few issues that users should be aware of - vignetting on full frame cameras is somewhat heavier then what one would expect from a medium telephoto prime and flare handling is simply awful. Despite these drawbacks, it's safe to say that the lens remains a mighty competitor on the market chock-full of macro lenses of various forms and shapes (focal lengths that is)...