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Sigma 18-50mm f/2.8 EX DC Macro

 
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Lab Test Results

  • Blur
  • Chromatic Aberration
  • Vignetting
  • Geometric Distortion
18-50mm $424
average price
image of Sigma 18-50mm f/2.8 EX DC Macro

SLRgear Review
June 4, 2011
by Andrew Alexander

The Sigma 18-50mm ƒ/2.8 offers a constant wide-aperture solution for APS-C-sized digital SLR cameras, an alternative to variable-aperture kit lenses. The lens has been replaced in Sigma's lineup by the 17-50mm ƒ/2.8 OS.

Designed to fit the APS-C sensor, the lens provides an effective field of view of approximately 28-80mm (Canon) and 27-75mm (Nikon and others). The lens was available in a variety of body mounts: Sigma, Canon, Nikon, Pentax and Sony. The Nikon version was upgraded to feature HSM focusing, to allow it full compatibility with its consumer bodies which don't feature a mechanical focusing screw.

The lens ships with a petal-shaped hood, accepts 72mm filters, and sits at around the $400 price point.

Sharpness
The 18-50mm ƒ/2.8 DC Macro offers good results for sharpness, better at the wide angle than zoomed in to 50mm.

Mounted on the Canon 7D, at 18mm and ƒ/2.8, the lens produces a small sweet spot of sharpness in the center of the frame, offering excellent sharpness there, and falling off to some light corner softness. As the lens is stopped down this corner softness slowly reduces, but never entirely disappears; it's a toss-up between ƒ/5.6 and ƒ/8 for the optimal setting at this focal length, trading central and corner sharpness in small degrees.

Zooming in provides similar results through the midrange (24-35mm), with a small aberration at 35mm and ƒ/4 which shows some exaggerated corner softness on the left side. We'll chalk it down to our sample, and other copies of the lens may not show these results, but it does reinforce the message to try to buy with a good return policy or be able to test thoroughly the copy you're aiming to buy. It's not a dealbreaker in this case, but it is noteworthy.

Wide open performance (ƒ/2.8) at 50mm is average; stopping down is definitely required to obtain better results for sharpness. At ƒ/8, we actually note slightly better results for sharpness than at results we found in the 24-35mm area.

Diffraction limiting sets in around ƒ/11, but this actually serves to even out the lens' performance, making the corners about as sharp as the center. In fact, performance is actually fairly good across the board at ƒ/11-ƒ/22, making it an excellent macro lens.

Chromatic Aberration
CA is nicely controlled by this lens, showing slightly at the wide angle, but reducing to very low levels as the lens is stopped down. The aperture choice doesn't appear to have any impact on results for chromatic aberration.

Shading (''Vignetting'')
Light falloff also isn't much of a factor for this lens; just a small amount when the lens is used wide open at ƒ/2.8. At 18mm, this produces corners which are a half-stop darker than the center; at any other focal length, it hovers at around a third-stop darker. At any other setting, the corners are below a quarter-stop darker, or practically insignificant.

Distortion
It's about what you would expect with a zoom lens of this range; barrel distortion on the wider end, and some pincushion distortion when zoomed in. Happily, distortion isn't extreme, and there is a point of parity around 26mm where the distortion effect is negligible. Wide-angle distortion isn't extreme at 18mm, and there's very little pincushion distortion to speak of above 26mm, either.

Autofocus Operation
Sigma uses an electrical motor for this lens, making it fairly fast and quiet, but Sigma's more recent HSM focusing motors are a bit quieter. The lens took about a second to go from infinity to close-focusing distance. The lens uses an internal focusing design, meaning the front element doesn't rotate.

Macro
The lens offers 0.33x magnification (1:3), making it a fairly decent macro lens. The minimum focusing distance is 20cm (just under 8 inches).

Build Quality and Handling
The lens is built with economy in mind, and features an all-black, all-plastic construction. The lens is coated with Sigma's rubberized coating, which offers good traction. There is a switch to enable or disable autofocusing, as well as a locking mechanism to restrain the lens to the 18mm zoom setting. The lens features a distance scale, but doesn't offer a depth-of-field scale. The lens mount is metal, and the 72mm filter threads are plastic.

The focus ring is mounted at the end of the lens, 3/8'' wide and composed of raised rubber ribs. The ring also includes the distance scale, etched in white and showing a scale in feet and meters; this whole assembly is about 3/4'' wide. The focusing range of the ring is fairly small, only 45 degrees, making manual focusing a bit tedious. We found that the focus ring has very little dampening, letting it turn very freely. The focusing throw is bounded on either side by hard stops. The lens will focus slightly past infinity. The front element doesn't rotate while focusing.

The zoom ring is the larger of the two, 3/4-inch wide, also composed of raised rubber ribs. There are around 45 degrees of rotation in the zoom ring, and a nice level of resistance to the ring; not too tight, and not too loose. There's no evidence of zoom creep, though Sigma has included a zoom lock just in case. There is some lens extension as the lens is zoomed in towards 50mm; about an extra inch of length.

The included lens hood is petal-shaped, adding a further 1 1/2 inches to the overall length of the lens. The interior of the hood is deeply ribbed to reduce the impact of any stray light entering the front element, and the hood can be reversed onto the lens for storage.

Alternatives

There's a fair amount of choice in this area; the only manufacturer which doesn't have a directly comparable offering is Sony.

Canon EF-S 17-55mm ƒ/2.8 IS USM ~$1,200
The Sigma lens can't compete with the Canon on sharpness, but in the areas of CA, distortion and corner shading, the Sigma shows somewhat better test results. The Canon sports optical stabilization and a slightly better range of focal lengths (a little wider, a little longer), but the price tag is much higher. Finally, the focusing system is of a higher quality.

Nikon 17-55mm ƒ/2.8G ED-IF AF-S DX ~$1,500
The Nikon 17-55mm offers only slightly better results for sharpness; results for CA and corner shading are a bit worse than the Sigma, and distortion is about the same. Nikon's AF-S focusing system, higher build quality and big price tag are the only other differences.

Pentax 16-50mm ƒ/2.8 ED AL IF SDM SMC DA* ~$900
We haven't yet tested this lens, but Pentax's offering in this area is the widest (16mm versus 18mm), at not a whole lot higher price.

Sigma 17-50mm ƒ/2.8 EX DC OS HSM ~$670
We haven't yet tested Sigma's replacement for the 18-50mm, but it's slightly wider and includes optical stabilization, and makes HSM focusing standard.

Tamron 17-50mm ƒ/2.8 XR Di II VC LD Aspherical IF SP AF ~$650
A perennial favorite, the Tamron 17-50mm was the first on the block and offers consistently good results. The Sigma is slightly sharper on the wide end, while the Tamron is slightly sharper at 50mm. Results for distortion and chromatic aberration are about the same, while the Tamron shows a bit more corner shading. The Tamron offers optical stabilization.

Conclusion
The Sigma 18-50mm ƒ/2.8 is a competent workhorse, probably finding its best application as a macro lens, where stopping down fully to ƒ/16 or ƒ/22 to get maximum depth-of-field doesn't rob too much sharpness from the image. The lack of image stabilization keeps the price low, and isn't missed terribly from this lens with its shorter range of focal lengths. There are certainly other options in this field, and if you don't want to spend top dollar, it's a good lens to consider.

Product Photos

Sample Photos

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.

Sigma 18-50mm f/2.8 EX DC Macro User Reviews

8.4/10 average of 12 reviews Build Quality 8.1/10 Image Quality 8.8/10
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  • 7 out of 10 points and not recommended by (12 reviews)
    Constant f/2.8 , Excellent IQ
    Bad QC

    I bought the lens "used". Excellent IQ , excellent optics.

    Construction is very good.

    But I found that my copy never communicate correctly with my S5Pro; 1 stop underexpose, 2 stops underexpose with flash (SB800), never provide the correct focal length data so my SB800 never autozoom with this lens, front focus.

    etc.

    Maybe, my bad luck. But this is my experience and my opinion.

    Sorry for my bad English.

    Update:
    I returned the lens and got an old stock non macro version.

    reviewed December 3rd, 2009 (purchased for $265)
  • 8 out of 10 points and recommended by (5 reviews)
    The macroability. Very sharp lens. Relative fast.
    Non, so far

    I got this lens with a Nikon D200. And I was surpriced of the picturequality. It is a very usefull lens. Fast, and with good macroability.
    I´m very satisfied, and a little surprised over the quality of pictures from a so "cheap" lens.
    Well done Sigma. Regards from Sweden.

    reviewed January 10th, 2009 (purchased for $350)
  • 10 out of 10 points and recommended by (1 reviews)
    Very sharp, even when wide open, good contrast, nice color, pretty fast AF
    No HSM

    I have this lens only a few hours... and I am very satisfied with it... Very sharp, even when wide open at 18mm and liitle less at 50mm. I strongly recommend it. I will use this lens for proffesional work. I also have Tamron SP 28-75 f/2.8. It is really sharp too, but less than SIGMA 18-50 dc ex macro.
    Regards from Belgrade, SERBIA.

    reviewed August 14th, 2008 (purchased for $518)
  • 9 out of 10 points and recommended by (1 reviews)
    Size, IQ, 2.8
    No HSM on Canon Mount

    I bought this lens recently to replace my kit lens. I looked at several alternatives, but decided to go with the sigma . I'm very happy with the image quality of this lens. It's a Sigma EX which I happen to like the build/construction of, but some don't. The 2.8 is great for inside pictures and pictures in lower light. All in all, it's a great lens. My only complaint is that i wish the Canon mount had the HSM motor. That being said, the AF is still quite fast and accurate and does not make that much noise.

    reviewed June 20th, 2008 (purchased for $420)
  • 9 out of 10 points and recommended by (1 reviews)
    Build Quality is good IMO, decent macro and AF.
    A bit soft towards the edges wide open.

    Bought the XTi body only and wanted a good standard zoom to replace the Canon 18-55mm but didn't want to spend $1000 on the Canon 17-55mm f/2.8's. Looked at the the Sigma, Tamron, and Tokina f/2.8's and decided on the Sigma. Haven't regretted it to date. Takes excellent pictures even at f/2.8, even though they are a bit soft....not a problem with the portraits I take.

    For anyone that wants a good constant lens at half the price of the Canon, this is the one.

    reviewed April 21st, 2008 (purchased for $419)
  • 8 out of 10 points and not recommended by (82 reviews)
    Wide angle macro and sharp if stepped down beyond 2.8
    Soft, soft edges and build quality is low IMHO

    I'm not going to recommend this lens, but this is my opinion.

    Photos speak for themselves. Here are samples taken with a Canon XTi:

    Sample Photos

    -Lex

    reviewed March 14th, 2008 (purchased for $430)
  • 8 out of 10 points and recommended by (2 reviews)
    Cover wide-standard zoon, better than kit lens
    Don't have HSM for Canon Mouth

    Decided to buy the wide-standard zoom lens next week but a big confuse between this lens and Tamron 17-50mm f/2.8 Di II LD Aspherical IF SP AF, don't know which one should I choose for my Canon 30D. Somebody can give some advice, thanks
    !

    reviewed October 15th, 2007
  • 5 out of 10 points and not recommended by (19 reviews)
    good center sharpness, good close-up peformance.
    horrible urine color , slow Af, very bad build ,deplorable edge sharpness.

    it is cheap in Thailand now, much cheaper than the Tmaorn and much less popular than the Tamorn.

    Well, I have the reasons why :
    1 it is so slow lens , I am talking about its AF.
    2 horrible edge and corner performance.
    3 prone to flare.
    4 horrible Sigma color cast.

    I hoped this can be my back-up lens for an event work , though I had to ditch it in a couple of days of free trial period.

    So I lost nothing , but now knowing that I will never touch any Sigma lens, period.

    I think this lens is mechanically horrible , the zoom ring is very stiff and hard to turn.

    The focus ring is so so hard to turn.

    The build is so bad , just using it for a couple of days changes its body color , the nasty distinctive touch of Sigma paint is almost gone by just playing around with it for an hour.

    I am sure the Canon EF-S17-55IS is a hundred times better lens than this, even after I dropped it on a hard ground , was fine , no damage , no scratch on it .

    You get what you pay for , indeed.

    If you are willing to pay to get the best , go for the Canon , if you need a bargain model , go for the optically excellent Tmaorn, though you will lose mechanical features of the amazing Canon lens; the IS, the USM , the FTM , the durable body.

    reviewed August 15th, 2007 (purchased for $340)
  • 10 out of 10 points and recommended by (5 reviews)
    very sharp, fast focus, nice feel
    none

    a really impressive lens. I was really surprised with the sharpness and color results. I would recommend this lens

    reviewed August 8th, 2007
  • 9 out of 10 points and recommended by (1 reviews)
    excellent color correction, very robust, smooth mechanics
    lens cap difficult to attach with lens hood attached

    I tested this lens with my Canon 400D and had direkt comparison with a Nikon 18-70 lens.
    The Sigma did beat the Nikon lens in many respects but I was not completely satisfied.

    The Sigma 18-50 provides very sharp images in the middle part of the picture all the way up to f/2,8.
    The outer parts of the picture, though, seem to be of worse quality than the Nikon which, in contrast, is not 100% sharp in the middle (f/2,8 - 4)
    My Sigma seems to perform better at 18-30mm than at 50mm (weird!?) where the images are a bit blurry towards the edges (f/2,8 - 4)
    Best results with aperture set at approx 6,7 - 9,5 - sharp images right to the edge.
    Closing the aperture to 13 and down to 22 does worsen the image quality again.
    Other positive impressions: No ghosts on nighttime shots in a city with so many bright light sources.
    Edges darken very little when the aperture is set at 2,8.
    Very good overall performance for a Zoom lens! Highly recommended.

    reviewed July 24th, 2007 (purchased for $489)
  • 9 out of 10 points and recommended by (1 reviews)
    sharpness, color practically everything
    lens creep, hood and cap problem as usual.

    A friend of mine urged me to try this lens and the tamron 28-70mm. The latter was out of stock so I decided to test this instead. 1st few shots and I was amazed by the color it produces that I had to buy it right away. 2 of my friends sold their 17-40 L lens and swtiched to this sigma so when I had extra money I had this in mind. No regrets. This lens delivers and makes my vr lens look baaad!!! IQ is at par or even better than one of those trinities.

    My only gripes are lens creep and the hood and front cap. Man this has always been the problem of Sigma. once you put the hood its so hard to put the lens cover back. you have to take off the hood 1st to put on the cover arghhh Hope next time it wont be an issue anymore.

    Bottomline this lens is a winner. Highyl recommended

    reviewed April 25th, 2007 (purchased for $500)
  • 9 out of 10 points and recommended by (1 reviews)
    Sharpness (even at f/2.8), contrast, build quality
    Distortion at wide end

    I sold my non-macro version of this lens to fund the purchase of a Nikon prime, and it's the only lens sale I ever regret! I've now bought a new copy, and at least it means I now have the new macro version, which seems even sharper than the non-macro version I used to have.

    This is a great walk about lens for when you want to go out with just one lens, 18-50 is a sensible range on APS sized digital sensors.

    Although it doesn't have USM, focus is fast and accurate - no front or back focus issues here. It's sharp - incredibly sharp by the time you get to f/4. Contrast and colour are both good too, and it doesn't seem to have the yellow cast that some Sigma's do.

    EX built quality is good as ever - this lens is well built, and substantial rather than heavy (it's heavier than a kit lens but not a neck-breaker). Focus and zoom rings are both well damped and a joy to use.

    The only slight downfall is distortion at the wide end, but that is easily corrected in Photoshop.

    I love this lens - highly recommended!

    reviewed January 19th, 2007 (purchased for $511)