Sigma 18-35mm F1.8 DC HSM "Art"

Conclusion

Ever since the industry-shattering announcement of the Sigma 18-35mm F1.8 HSM "Art," we couldn't wait to get our hands on a copy. Month after month of delays and pushed back release dates it finally arrived, and what an exciting time it was. This is especially true since by the time it was released for Pentax, an abundance of reviews had already been published with promises of sharpness never before seen in a zoom lens.

Our expectations had been met - outstanding sharpness and clarity are certainly not just talk and the constant F1.8 aperture affords us new opportunities that we didn't have before. This is all the more true and critical for K-mount aficionados considering how Pentax doesn't have a lens faster F1.8 or faster wider than 31mm. And that lens will set you back over a grand.

What was surprising to us was how well the HD 20-40mm F2.8-4 Limited lens kept up and how poorly the legendary FA 31 Limited performed. Except for wide open at 20mm, the Limited zoom seemed to meet the 18-35 every step of the way with the FA 31 being more than just blown away, especially wide open.  Truly a credit to both zoom lenses and not meant as disparaging to either, but it elevates our standard and expectations for future lenses and proves that Pentax is just as capable of producing world-class glass (albeit at a premium in the case of the Limited zoom). But then this also raises the question of who the Sigma is meant for.

In true Pentax fashion, if you favor compactness and "masslessness," the "Art" zoom is not for you. It's big, heavy, and will certainly be something to deliberately bring rather than just absent-mindedly being thrown in a jacket pocket or corner in your bag. But this is expected - speed in a zoom comes at a price, and weight and size aside, for under $800 (USD) MSRP we can't think of a better value if the physical attributes aren't a hindrance to your photography.

Also, there's two design features that we have an issue with. First, we really can't understand why Sigma didn't weather seal this lens. By the nature of its physical construction it's already pretty much there - internal zooming and focusing. And with how tight the tolerances are, we honestly think the only thing that is holding it back is the lack of a gasket on the mount. Again, coupled with the K-3, this surely would have been the de-facto standard for photojournalism type work. The other thing is the focal length, particularly on the wide end. We would have loved for it to be 16-30mm, as the 2mm extra on the wide end makes a massive difference in cramped locations (i.e. indoors). At 18mm, it's hard to justify it as a standard zoom, regardless of the aperture. We realize that both of these are in a perfect world, and it takes absolutely nothing away from Sigma's momentous achievement, that it deserved mentioning if there ever were a Mark II version of this lens and how to improve it. We cannot emphasize enough that this takes nothing away from our being impressed with what Sigma's team has accomplished.

We wish that could be the end of our review and rate this lens the highest of any zoom we've ever had the privilege of assessing (and it would have been by a landslide), but it just wasn't meant to be. The caveat to what would have been a glowing review is simply the abysmal autofocus performance. There's not much more to say than what was already noted in detail on the Autofocus page. We really meant how we have never had such a breakdown of confidence in a lens' ability to attain accurate focus in any situation, with any aperture, at any focus distance. Hopefully Sigma takes note and addresses this issue soon so users don't have to feel like they are rolling the dice on whether they get a lens that focuses or doesn't in spite of their advanced cameras.

Pros

• Constant F1.8 aperture throughout zoom range
• Excellent build quality throughout the lens' construction
• Large focus and zoom rings are perfectly dampened and easy to find and grasp
• Capable of shallow-depth of field wide angle portraits
• The only fast and wide angle solution for Pentax's many fast/wide holes between 18 and 30mm
• Very low coma
• Excellent resolution, including from wide open - starts significantly sharper than FA 31 Limited
• Negligible distortion thanks to the many distortion-correction glass elements
• Vignetting reduced to effectively negligible amounts after 1/2 stop
• Wide angle and fast aperture allow for creative portraits
• Autofocus is very fast and nearly inaudible
• Perfectly accurate autofocus, regardless of aperture, when using Contrast Detect AF (Live View)
• Excellent aberration control with very low amounts of purple fringing
• Excellent contrast and vibrant colors, particularly when stopped down
• $799 MSRP makes it an outstanding value, especially compared to the FA 31 Limited
• Beautiful and creamy bokeh, particularly with flowers
• Full-time manual focus override
• Capable of pseudo-environmental-macro images
• Included high quality lens hood securely reverses for storage in a minimal, space-saving manner
• Compatible with Sigma USB Dock

Cons

• Not weather-sealed despite excellent build quality and both internal zoom and focusing
• Dreadful autofocus accuracy when using PDAF (looking through viewfinder)
• Bokeh can be jarring with highlights, producing "frog-egg" or "donut" ring bokeh
• Stark color, temperature, and contrast shift from wide open to stopped down
• Very large and makes your camera front-heavy; particularly troublesome on tripods
• Zoom range not optimal for event/indoor photography as a standard zoom; 16-30mm much better
• As a third-party lens, does not support Pentax in-camera lens corrections
• Due to length, only compatible with on-board flash at 35mm and without hood
• Disappointing flare control

Rating

*preliminary result, pending further investigation as noted on the AF page

Details on our lens rating scale are available at the bottom of our review homepage.

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