Sigma 17-70mm f/2.8-4.5 DC Macro AF Lens User Report

A Better Kit Lens?

[ Our "User Reports" are observations by the user of an actual production unit in what can be considered normal use by a "serious user". We avoid the term "review", since the product is not put through the rigorous repeatable test systems and conditions of a product review. We do make pains to ensure, by offering as detailed a report as possible, that these are no less informative than a formal review. ]

Sigma has once again thrown a challenge down for DSLR camera manufacturers with their new 17-70mm f/2.8-4.5 variable aperture digital-only zoom lens, which tries to outdo the "kit lens", the ubiquitous 18-55/3.5-5.6 lenses often bundled as kits with Canon, Nikon and Minolta/Sony DSLRs that share similar APS-C crop factors. Sigma's offering outdoes the kit lens on a number of fronts: the focal lengths on tap go wider (up to 17mm) and longer (up to 70mm), the apertures larger (2.8-4.5 versus 3.5-5.6), and the focusing close enough to nearly deserve the "Macro" badge.

Where it runs into some stiff competition is when it is compared to the Nikon 18-70/3.5-4.5 DX and another of Sigma's own offerings, the Sigma 18-50/2.8 EX DC.

Build Quality

Put side by side, you would not easily be able to distingush the 17-70 from the 18-50/2.8, as they are similarly proportioned. The Sigma 17-70 is made of tough plastics and coated in an EX-like crinkle finish. Focal length and other markings are printed on, as with the 18-50/2.8, and the zoom and focus ring are wrapped in textured rubber similar to the 18-50/2.8. Likewise, the lens thread and mount are also made of metal and not plastic.

The lens thread, though, is bigger at 72mm, and the lens barrel extends a fair bit more than the 18-50mm/2.8, owing to the greater range of focal length and the wider wide end. There are printed-on reproduction ratio markings denoting the macro ability of this lens. So far there is no sign of lens creep, but it has a locking mechanism anyway, that keeps it at the widest setting for storage.

Leaving comparisons with its sister lens for a moment, the Nikon 18-70 DX, the nearest Nikon equivalent, comes in similarly proportioned and with similar but different build. The 18-70 arguably feels less sturdy, not surprisingly because the 17-70 seems to be built so much like an EX lens.

The Sigma 17-70 comes with a plastic lens hood in the same EX-like finish, Sigma front and rear end caps, and a padded lens bag that looks like a dead ringer for the 18-50/2.8 lens bag except for the non-EX Sigma badge.

Handling

In terms of handling, the Sigma 17-70 offers just a little more than is needed to stack up well against the kit lenses. There is no M/A focusing mode to allow quick focus corrections, and the focus ring rotates as the lens autofocuses. It does not have silent motors (HSM in Sigma terms), so the lens is a little noisy and the focusing only just fast enough not to be a hindrance for fast focusing. There is no aperture ring, but this will not be missed by most digital photographers.

It does show up the kit lenses on some important counts. The lens features internal focusing, which means the front element does not rotate while focusing, so use of a circular polarizing filter is not a pain. A minimum focusing distance of 0.20m means the lens easily focuses closer than the kit lenses, the Sigma 18-50/2.8 and the Nikon 18-70.

The Sigma 17-70 is a variable aperture lens, so the available maximum apertures change at different focal lengths as you can see below:

Focal Length	Magnification (1:x)	Max Aperture
17mm	4.7	f/2.8
		f/3
		f/3.2
24mm	4.2	f/3.3
		f/3.5
35mm	3.5	f/3.8
		f/4
50mm	2.8	f/4.2
70mm	2.3	f/4.5

As show above, the Sigma 17-70 is not f/2.8 for much of its range. By 24mm you are already at f/3.3, and by 50mm at f/4.2. This is no worse than with the Nikon 18-70 DX, but will leave those with the need for faster apertures slightly disappointed (in truth they would be better served by a constant aperture lens).

Image Quality

The Sigma 17-70 shares the same characteristics as the 18-50/2.8: it is sharp at all apertures at the center, then decreases in sharpness in the corners. Moving into the longer end of the focal lengths, the difference between corner and center sharpness decreases. As is the case with some macro zooms, sharpness at infinity focus tends to be soft. Here it is not bad but not great either. Bokeh is not very smooth but not that distracting. These traits make it a serviceable enough macro lens, as long as you do not need 1:1 reproduction, and a very flexible lens able to deliver sharp photos in general use.

[ Nikon D50 and Sigma 17-70mm f/2.8-4.5 DC Macro ]
[ 1/100s f/11 70mm ISO400 ]


[ Nikon D50 and Sigma 17-70mm f/2.8-4.5 DC Macro ]
[ 1/250s f/2.8 17mm ISO400 ]


[ Nikon D50 and Sigma 17-70mm f/2.8-4.5 DC Macro ]
[ 1/100s f/8 70mm ISO400 ]

Some flaws in this lens can be found if you look hard enough. Vignetting shows up at the wide apertures, and at the same time contrast suffers noticeably. Also, chromatic aberration is obvious at wide open apertures, and still noticeable even stopping down to as much as f/11 if the conditions are bad enough.

Compatibility

The Sigma 17-70mm f/2.8-4.5 DC Macro is available in Nikon, Canon EF-S, Pentax and Minolta/Sony mount, as well as in its "native" Sigma mount. Being a DC lens it is not recommended for use on full frame DSLRs since it is built for cameras with APS-C sized sensors.

Conclusion

The Sigma 17-70mm f/2.8-4.5 DC Macro seems to have been made to a simple blueprint: take the common digital kit lens, and make it better. For the most part, it is. It only suffers for being compared to its sister lens, the Sigma 18-50/2.8, and the Nikon 18-70/3.5-4.5 DX. In light of it being so similarly priced to a constant aperture lens and a similar offering from Nikon, this super-kit lens becomes a hard sell as an upgrade to the bundled lens. In truth, we would be more forgiving if it approached the prices of the digital kit lenses that it trumps so comprehensively.

For more concise technical reviews, check out:

PhotoZone reviews the Sigma AF 17-70mm f/2.8-4.5 DC Macro

[ Sample photos were shot with the lens being reviewed, attached to a Nikon D50 digital SLR. Photos of the product were shot with a Sony V3. ]

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