Sigma 18-50mm f/2.8-4.5 DC OS HSM

Sigma 18-50mm f/2.8-4.5 DC OS HSM User Reviews

• 9 out of 10 points and recommended by Alexsoox (1 reviews)
  Cheap,Sharp

  Not full range f/2.8

  This is a great lens for two hundred bucks. The construction is very nice. Very sharp at over f6. Compare to the Nikon 35mm/1.8 at ~25-40mm f6-11 is very hard if not impossible to tell the differents at the computer. I was a little worry ordering this lens since a lot of people complain about front and back focus. I been a film guy for over 20years and this is my first Digital SLR lens. Very nice contrast and color too. Wish it came with the Sigma lens bag.

  reviewed March 19th, 2010 (purchased for $200)
• 10 out of 10 points and recommended by zoro02 (4 reviews)
  Affordable, sharp at F4 - 8, OS worked, closeup/macro is a bonus @ 20cm, non rotating zoom

  Soft @2.8, nothing else ATM until I run a field test

  I just got the lens and took some picture with hot shoe flash at night, this is what I think about the new Sigma 18-50 F2.8-4.5 OS HSM
  
  1) Build - Can't be compared with Tokina but acceptable
  2) Zoom ring - damped well controlled
  3) IQ - pretty sharp even at f4. Very sharp at f8
  4) Bonus - closest distance approx 20cm, can be use for closeup/macro which was NOT advertise as a feature. When I add 2x teleconverter, this will give me macro effect.
  
  Will post image in flickr sometime this week. Overall I'm very satisfied especially $$/quality features.

  reviewed March 15th, 2010 (purchased for $270)
• 9 out of 10 points and recommended by ksbuehler (4 reviews)
  light, inexpensive, 18mm @ f2.8 with stabilization, HSM

  a bit of Chromatic aberration, focal field curvature

  I concentrated my tests on performance at F2.8 and 18mm, as that is what I care about. I have a 45mm TSE 2.8 and 70-200mm F4L IS to cover other focal lengths.
  
  For the price, this lens is great. I wanted a wide lens for use in low-light without a flash on my Canon 20D. This is the least expensive f2.8 18mm lens on the market with stabilization.
  
  Weighing only 400g, it is also the lightest stabilized 18mm f2.8 lens on the market. Size and weight are big factors for me. I fly internationally for business quite a bit, and prefer to travel carry-on only. Between dress shoes and business clothes, not much room for my photo gear.
  
  As a bonus, it uses the same 67mm filters as my 70-200mm f4L IS.
  
  The 18-50 lens does not rotate or extend during focusing and zooming. Great!
  
  Build feels pretty solid.
  
  The HSM is NOT full time manual. I've been pampered by my Canon L lens so this was unexpected. I'll get over it.
  
  
  I used a few USAF 1951 test targets to measure resolution performance from f2.8 through f11. Sharpness is nearly as good across the frame at f2.8 as f8.
  
  Be aware there is noticeable field curvature at f2.8 and 18mm. (I'm talking about the curve of the focal plane, not barrel/pincushion distortion). If you focus on a perfectly flat wall at f2.8 @ 18mm, either the center of the image will be in focus, or the corners, not both. In the real world, a curved focal "plane" is not usually a problem. Most of my shots are not of a perfectly flat object that is perfectly parallel to the sensor plane. I'm not sure how slrgear, or any other site, can account for this in their tests. My method is to step through a few focal distances to check quality of focus in the corners.
  
  The optical stabilization works well at 18mm. I can shoot at 1/15 with nearly 100% of shots being very sharp. At 1/8, it's more like 30~50% of shots very sharp. It seems to depend even more on how much coffee I've had so YMMV.
  
  At 18mm, there is chromatic aberration present in the corners at all apertures tested (f2.8 to f11). It appears to be consistent across all corners, indicating that it could easily be removed in s/w. Further, the CA seems fairly consistent across apertures from f2.8 to f11. I have not tested software correction of the CA yet nor have I checked CA performance at other focal lengths.
  
  There is about 1/2 stop vignetting near the corners at 18mm and f2.8. From reviewing test data for other lenses, this is better than the Canon 17-55 2.8 IS, Canon 16-35 2.8, Sigma 18-50 2.8 EX DC. It is about the same as the Tamron 17-50mm 2.8 XR Di II.
  
  Macro performance. I put on a 12mm extension tube. Working distance is 0" at 18mm, 1" at 28mm, 2" at 35mm, and 4" at 55mm. The frame width is 1.3" at 18mm, 1.4" at 24mm, 1.5" at 28mm, 1.75" at 35mm, and 2.1" at 55mm. Using Canon 20d, followed by Canon 1.4 II TC, followed by 12mm ring, followed by Sigma 18-50 2.8-4.5 gives a 1" frame width at 55mm. 20d+1.4x+20mm tube+Sigma gives 0.75" frame width at 55mm.
  
  Next things on this lens to test, not necessarily in this order:
  1) 28mm performance and Optical stabilization performance
  2) optical stabilization in 55mm macro configurations
  3) 45mm performance vs my 45mm TSE

  reviewed September 15th, 2009 (purchased for $300)