Sigma has definitely been on a roll. A few years ago they awoke from their third party slumber and realized that they were capable of making better products than what they were currently building. Clearly a decision was made to target a more premium place in the market, and so they scrapped their existing design philosophy entirely along with their marketing strategy. Whoever came up with their new “Global Vision” marketing strategy deserves a raise, and the team that came up with their new design ethos deserves an even bigger one. Sigma lenses still have their quirks (more on that in a moment), but they are building the handsomest lenses on the market. I have now reviewed lenses from all three categories of Sigma’s Global Strategy (Art, Sport, and Contemporary), and despite still not having a clue what “Contemporary” is supposed to mean in this context, I can attest that the cosmetic design and general construction of all of these lenses is excellent. But Sigma has also demonstrated the ability to think outside of the box and take a few chances. That is definitely true of the lens being reviewed here, the Sigma 18-35mm f/1.8 DC HSM ART lens.

Yes, that isn’t a typo! This is a zoom lens with a constant maximum aperture of f/1.8, making it a completely unique lens in the current market. It has been an unspoken rule of sorts that zoom lenses generally have a maximum aperture of f/2.8 (I currently own three that follow this “rule”), and the understanding was that the physics of building a zoom lens with a larger aperture than f/2.8 would produce a lens larger, heavier, and more expensive than photographers would be willing to bear. The 18-35ART isn’t small or light, but neither is it exceptionally large or unwieldy. It is slightly longer than Sigma’s own 24-70mm f/2.8 (4.76” vs. 3.7”) and marginally heavier (811g vs. 790g). Its specs are almost identical to those of Canon 24-70mm f/2.8L II (the Sigma is 8mm longer and 5 grams heavier). This lens is a bit longer but narrower than most 24-70mm designs.  It might feel a bit front heavy on smaller consumer DSLRs, but balanced nicely on my “prosumer” 70D.  The same would be true for the more robust bodies from any of the camera systems that this lens is sold for (Canon, Nikon, Sony, Pentax, and Sigma).

Sigma hedged its bets with this somewhat radical design by using a fairly small zoom range and designing a crop sensor only (APS-C) lens. So no, this lens doesn’t really work on a full frame body (more on that a little later). The success of this lens has allowed Sigma to greenlight a somewhat similar full frame lens, although that lens (a 24-35mm f/2) has a smaller zoom range,  a slightly smaller aperture, and is a bit heavier (+130g). The 18-35mm has a full frame (35mm) equivalent focal length of 28.8-56mm (on a Canon). The focal length equivalency will depend on what system you are using and its crop factor. Canon (reviewed here) has a 1.6x crop factor. On a Nikon, Sony, Pentax, or Sigma body the crop factor is 1.5x and the lens will have an equivalent focal length of 27-52.5mm.  The two shots below give you an idea of how that zoom range looks like in real life:

There are two ways to look at these unique lenses, and how you judge them will ultimately come to down to whichever point of view you ascribe to. You can look at these zoom ranges as being so marginal that they offer little advantage over equivalent primes (zoom a few steps with your feet) or as being somewhat like getting multiple prime lenses (because of the large aperture) in one. If you take the former view, this lens will seem large and expensive (Sigma makes a very popular 30mm f/1.4 ART prime for crop sensor bodies that is half the size, weight, and price). If you take the latter view, this lens will seem like a convenient bargain…but only if it delivers in the optical department. (A clue – it does!) This lens covers important focal lengths like 18mm (28mm FF), 24mm (right around 35mm FF), and 35mm (50mmish FF), and covers them all quite effectively.

The 18-35 ART has Sigma’s increasingly familiar (yet still excellent) new design ethos. It is black on black, but with very elegant contrasts achieved through textures and finishes. Both the focus and zoom rings are nice and wide (one advantage of the long lens barrel) and both are also beautifully damped. This is an internal focus and internal zoom design, and they typically have the smoothest zoom action in my experience. This lens has a very premium feel and I have waxed eloquent in other Sigma Global Vision reviews about the look of the lenses and the quality of the construction. All I can say is, “Great job, Sigma!”

Internally the lens is 17 elements in 12 groups and has a 72mm filter thread. This filter size is shared with a number of Canon primes and is easy to find and reasonably inexpensive. The front element does not rotate during focus, so feel free to throw a polarizing filter on there! The lens has a 11” (27.94cm) minimum focus distance with a resulting maximum magnification of .23x at 35mm, which is a useful figure that compares favorably with its various competitors.

Image Quality

Anyone who has used one of Sigma’s ART series lenses will not be surprised to me hear me say that the optical performance is exceptional.  Sigma has found a way to consistently produce optical excellence with this series, and the 18-35mm is no exception.  For Canon users the top EF-S zoom lens has long been the 17-55mm f/2.8. It has a robust build, constant aperture, and better optics than most other EF-S lenses. Compared side by side, however, and the Sigma destroys the Canon in sharpness and contrast. The Sigma is sharper at f/1.8 than the Canon is at f/2.8 across the image frame, and stopping the Sigma down to equivalent apertures only makes it more obvious. I recommend taking a look at The Digital Picture’s comparison tool here to get a better sense of just how clear the difference is in chart testing.

As many of you know, I don’t do chart testing, but the optical excellence of this lens was clear in field use.  There is very little to criticize.  Vignetting is quite low on the lens and compares favorably with most primes covering similar focal lengths.  The lens is not particularly flare resistant, and will produce a bit of ghosting when the sun is directly placed in the frame.  The resulting artifacts are fairly artistic, however, and this is far from the worst offender I’ve seen in this regard.  This video will give you an idea of the lens’ reaction to the sun being placed in the frame.

This was shot at f/11, and so also gives you a look at a strength for the lens – the nicely defined sunstars/sunbursts that it produces.  That makes me think that you will probably want to take the risk and put the sun in the frame periodically!  Chromatic aberrations are quite well controlled, and while the lens has the typical barrel distortion on the wide end of the zoom range and some pincushion on the long end, neither is extreme enough to really get your attention in field use. Lens sharpness is excellent.  I’ve not often been blown away for the optical performance of crop sensor zooms, but this is an exception to the rule.  It is very sharp even wide open, and that sharpness extends across the vast majority of the frame.  This is true throughout the focal range.  It is apparent that Sigma stuck with the focal range they could do very well and went neither wider nor longer.  The zoom range is limited, yes, but optical performance is not compromised at any point of it.  Color rendition is also excellent.  There were a number of images that just delighted me right out of the camera.

The lens is also capable of producing nice bokeh.  The transition from focus to defocus is nicely smooth, and the rounded aperture iris ensures that bokeh highlight circles remain round even when the lens is stopped down multiple stops.  Here are few unedited bokehlicious shots for you:

The focal length isn’t particularly long, so you will need to be fairly close to your subject to really blow a background out, but the nice sharpness combined with good bokeh performance means that images will have a reasonable three dimensional effect.  Without getting too technical, know that the depth of field is different between a full frame and a crop sensor body.  The larger the sensor the more narrow the DOF at equivalent apertures.  Put simply, f/1.8 produces a more shallow DOF on a full frame sensor than f/1.8 on a crop sensor.  The f/1.8 aperture helps here, however, and for a crop sensor lens this is one of the better performers (in this focal range) for producing shallow DOF.

The lens also has a very useful .23x maximum magnification (nearly 1:4 life size) meaning that you can get close to things and produce reasonably pseudo-macro results (macroish?).  This compares very favorable to a lot of 50mm lenses and their typical .15x magnification.  Even better is the fact that the lens continues to produce very sharp images at its minimum focus, although you probably will want to stop it down a bit for maximum sharpness and appropriate depth of field to your subject (f/1.8 is very shallow at minimum focus range).

I own the newest Canon mirrorless body (the EOS M3).  While it has a few clunky aspects (some of which are unique to small mirrorless bodies and some of which are unique to CANON mirorless bodies), the sensor in it is pretty spectacular (the best crop sensor that I’ve encountered personally).  I used the Canon EF to EF-M adapter to mount the 18-35 ART on the M and give it a shot.  The lens is obviously very large and heavy for such a body, so this is certainly not a match made in heaven.  The image quality, however, was fantastic, although I found the autofocus very leisurely (more so than most of my other lens used through the adapter).  Still, if you own a similar mirrorless body/adapter and you have some time on your hands, you can get some nice results like these:

On a mirrorless body, however, a small native prime like my EF-M 22mm f/2 STM makes a lot more sense, offering similar image quality and aperture value.  Again, however, if you have a body and an adapter to make it work, it is an option.

Finally, due to the nature of the Sigma’s mount, it is possible to mount the lens on a full frame body.  Just know that it is only really useful at the 35mm end of the focal range.  18mm looks like this mounted on my EOS 6D body:

Yuck!

The 35mm is far more presentable, however, and other than some vignetting and additional distortion, it is very usable.

I certainly wouldn’t recommend buying this lens if you only have a full frame body, obviously, but if you happened to also have a full frame body and didn’t have a 35mm prime this might prove a useful bonus.

All in all this lens is at the top of the heap for optical performance in a crop sensor lens.

AF Concerns

Every time I review a Sigma lens I will be closely looking at the AF (autofocus) performance. I’ve rarely had a problem with HSM motors when it comes to sound or speed (they are amongst the quietest focusing lenses that I’ve encountered and generally quite fast), but I have major concerns when it comes to AF accuracy and consistency. The Sigma 150-600mm Sport was the first Sigma lens that I walked away completely satisfied from when it came to its AF performance. I’m afraid the 18-35mm ART didn’t impress out of the box. My review body is a Canon EOS 70D, and trying to use my typical AFMA program (Reikan FoCal) produced such variation that an automatic calibration simply didn’t work (the program gave up). I did a semi-automatic calibration using my own eyes, and discovered why. Just when I thought I had a value zeroed in, the results would jump around. The focus peak looked like a yo-yo. I’ve never had such a difficult time calibrating a lens before.

After wrangling with it for a while, I feel like I got the correct AFMA values. The question is whether or not those will remain the correct AFMA values. My focus accuracy certainly improved with the current settings and I intend to keep a close eye on focus accuracy throughout the review.

I was not blown away with the lens in AF Servo mode either. The 70D has a relatively robust AF system, but when I got my dog to charge towards me I felt my focus accuracy was about 25%. The lens seems to like single shot AF better.

I find that portrait shooting is perhaps the most demanding type of photography I do for autofocus accuracy, and despite feeling that I have the correct AFMA value for the lens I was still disappointed with my overall focus consistency. I mostly shot at f/2 for the portrait session, and when carefully examining my results I found that about 60% of my shots were well focused, another 20% were acceptably focused, but 20% were not focused well at all. When the lens was accurately focused, the results were quite nice (see the sharpness in the final crop!)

I use a tool in Lightroom called “Show Focus Points”, and it shows in an overlay the information the camera recorded regarding autofocus at capture. Here are some samples that show the inconsistency I am speaking of. You will note that in every case the lens/camera reported accurate focus lock, but the actual focus is inconsistent.

In this case, the camera/lens shows accurate lock, and the image is accurately focused.

In this example the camera/lens reports accurate lock, but the image is front-focused by a fair margin (might be acceptable for some).

Finally, in this example the camera reports the same, but the image is terribly backfocused and is a wasted shot.

This is pretty hard to accept when I am accustomed to coming home from a wedding with 700-1000 shots taken with my own kit and typically won’t have to discard one shot for missed focus.  Some report that their copy of the lens consistently focuses accurately, but others report similar frustrations with inconsistent focus results.  Put simply, I think there is copy variation, and the fact that I reviewed a new retail copy some 2 years after the release date of the lens tells me that Sigma hasn’t been able to completely nail down this issue.

The lens seemed to do best within about 8 feet, but in the crucial portrait window of 8-15 feet (for full body shots) the focus accuracy dropped dramatically. This reveals one of the problems I (and others) have experienced with the lens. You can set an effective microadjustment value for a certain distance, but that value may not be the right one for other distances.

I should add that I am a pretty accomplished portrait photographer. I’ve shot thousands of portraits with far more wide aperture lenses (as a reviewer) than what most photographers ever have opportunity to use. I shoot portraits with autofocus lenses, manual focus lenses, and even vintage glass. I know what I’m doing, so I know that this isn’t a matter of user error.

When focus is nailed, this lens is exquisitely sharp. Live view results (particularly with the DPAF on the 70D) are better (in terms of focus consistency), but I don’t really use Live View for portrait work very often and prefer not to. My experience with Sigma lenses say that some of you will be perfectly satisfied with your copy and it will give fabulous results; others will experience inconsistent results as I did. My recommendation is to thoroughly test your copy and make sure you have one that will calibrate well on your body. I think the lens is worth the trouble.

The use of Sigma’s USB dock will help somewhat, as it enables you to tune focus for several specific distances.  There will be a learning curve as you learn how to properly utilize the dock (an additional $60 charge), but my feeling is that it is worth the effort to get the best results from your lens.  The USB dock will also enable you to load firmware updates to your lenses (helping to prevent incompatibility issues with future bodies) and will also work with most other newer lenses from Sigma.  I’m a bit of a tech guy, so I personally think this is pretty cool.  I didn’t have a Sigma dock for this review (I’ve reached out to Sigma to provide me one for future reviews), but I would have been interested to see how much of a difference tuning the lens in this way would have made.

A final footnote is that I hear far fewer complaints coming from Nikon and Sony users than I do from Canon shooters.  My guess is that Sigma autofocus is probably at its worst on Canon bodies.  All third party manufacturers have to reverse engineer autofocus algorithms, but my experience is (at least for Canon) that Tamron has this better figured out than Sigma.

If you can overcome this hurdle with your copy of the lens, you are golden.  It has beautiful optics that are going to make you smile time after time.

Glass Half Full/Glass Half Empty

I encourage you to watch the video review of the lens for a more interactive look at my findings.

As I said earlier, there are two ways to look at this lens. Before examining those, however, let me first say that this is undoubtedly one of the finest crop specific lenses out there. APS-C has received relatively little development dollars from most manufacturers and as a result APS-C lenses tend to be budget options with variable apertures. This lens is as lovingly designed as other Sigma ART series lenses, and thus it is the Cadillac of crop sensor zooms. I’m happy that such a lens exists. It does indeed exist…should you buy it?

One argument is that the limited nature of the zoom range essentially makes this a very large prime lens.  There are cheaper, smaller, and lighter alternatives. Then again, Sigma’s own 50mm f/1.4 ART is essentially the same size and weight and people LOVE it (focus issues aside).  We live in a day of large primes, and the reality is that that this lens is far sharper than any crop specific prime lens in this focal range.  Sigma’s own 30mm f/1.4 ART lens doesn’t hold a candle to this lens optically (surprisingly).  I think the best way to rationalize this lens is to consider it more like three important prime lenses in one zoom lens.  It has prime quality (better than prime?) at wide open apertures and gives you the flexibility of changing your framing (though in a somewhat limited fashion).  It works nicely at wide apertures, of course, but then also becomes a very nice landscape/general purpose lens stopped down a bit.

In conclusion, this is a groundbreaking lens no matter how you look at it, and I applaud Sigma for taking a chance and thinking outside the box.  I do feel that it is has paid dividends here.  The image quality from the Sigma 18-35mm f/1.8 DC HSM ART lens is exceptional in every facet, and the fact that Sigma managed to go a full 1 1/3 stops wider than other zoom lenses while still nailing the image quality is a huge achievement in engineering.  The next review on my list is the brand new full frame 24-35mm f/2 from Sigma.  Sigma’s Achilles’s heel of focus accuracy persists with the 18-35mm, but I do think that many people will find the lens good enough to endure a little tweaking to get it right on your body.  Pair this lens with a good telephoto and you would have an excellent kit that would offer premium image quality on the great APS-C bodies available to consumers right now.  Above all, though, I commend Sigma for taking some chances and swinging for the fences.  I’m reminded of the quote from Norman Vincent Peale, “Reach for the moon.  Even if you miss, you’ll land among the stars.“

Pros:

• Exceptional image quality wide open that extends to the edges of the frame
• Extremely low vignetting
• 1 1/3 stops more light gathering at f/1.8 than other zooms at f/2.8
• Beautiful lens design and build.
• Internally zooming and focusing
• Smooth, nicely damped focus and zoom rings
• Includes nice padded case

Cons:

• Large (essentially the size of a full frame 24-70mm f/2.8 lens)
• One of the more expensive crop sensor lenses at $800 USD
• Can exhibit inconsistent focus accuracy
• Limited zoom range
• Flare resistance isn’t exceptional

Alternatives

I’ve mentioned both the Sigma 30mm prime ($300 cheaper and has a slightly wider aperture at f/1.4) before along with the Canon 17-55mm f/2.8 (constant aperture [though a 1 1/3 stop slower] and a larger focal range) as alternatives.  A third alternative is the Tamron 17-50mm f/2.8 VC.  It has some the same advantages of the Canon but is considerably cheaper ($150 less).  They both have effective image stabilization systems that help to make up for the smaller maximum aperture. If absolute image quality is your goal, however, the Sigma 18-35mm is by far the best of the bunch.

Gear Used:

Canon EOS 70D
Sigma 18-35mm f/1.8 DC HSM ART Lens
Adobe Lightroom CC Software for Mac and Windows (Boxed Version)
Adobe Photoshop Creative Cloud 1-Year Subscription
Alien Skin Exposure 7 (Use Code “dustinabbott” to get 10% anything and everything)

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