Sigma 18-35 f1.8 DC/HSM
Sigma 18-35 f1.8 - A Great Lens
I have just finished a week of shooting with the new Sigma 18-35 f1.8 DC/HSM on a trip to Oregon. I used the lens on a Sigma SD1 (non-M), shooting a mixed bag of hand-held and monopod. Weather was very good with lots of clouds and clear air. Although there were brush fires to the east and west, I was fortunate that there was very little, if any, haze when I was shooting.
Specs: The lens is heavy, tipping the scale at 28.6 oz (810g), making it 10 oz heavier than the 8-16. It features a hefty 17 elements in 12 groups, a constant maximum aperture of f1.8, and a minimum aperture of f16. The minimum focusing distance is 11 inches (28cm) with a magnification of 1:4.3. It is an internal focusing (IF) lens and the lens stays the same length at all focal lengths and focusing positions. The only "button" on the barrel is the AF/MF switch. Both zoom and focus are firm - neither too stiff nor too loose. It feels very well-made.
AF: Auto focus was as would be expected with the lens on the SD1. No better and no worse than Sigma's more recent wide zooms (8-16 and 17-70). Distant low-contrast scenes were problematic on the wide-end and not so bad on the long end. The good news is that at infinity, the focal point does not appear to shift when zooming, as happens with older zooms. The net is that (at infinity), you can put the infinity mark on the focus line and the image will be in focus. This is reminiscent of the older lenses whose focus stopped at the infinit mark.
IQ: Most of my shooting was done at f8. The images were very sharp at all focal lengths. Corners/edges were very well preserved even at 18mm - noticeably better than the 8-16 and 17-70. At 18mm/f1.8 the images were sharp in the center with some softening of the corners but nothing that could not be lived with (see Samples Gallery). Sigma seems to have solved the corner issues with this lens. I did not shoot wide open at any other focal length. CA seems to be very well controlled. All images had sharpening set to zero in SPP and were not sharpened in Photoshop.
The Samples Gallery contains images by focal length. It is in the Sigma Users Group gallery on Pbase:
Click on the Lens Gallery button and then Zoom Lenses. The galleries are in ascending order by focal length.
All in all, the 18-35 is a superb lens, and is Sigma's best wide zoom to-date by far.
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