| Latest Review Posted | Sigma 17-70mm F2.8-4 DC Macro HSM (Contemporary)
I was looking for a lens to replace my 18-55 WR on Pentax K-5, and I initially chose Sigma 17-50 F2.8. Unfortunately (or maybe fortunately?) it was out of stock, so I had to buy this cheaper one. I compared it with 18-55 using JPEG, tripod, and manual focus under good light:
The build quality is good enough IMO, though it is just a Contemporary lens, neither an Art nor an EX. One big difference from 18-55 is that the friction of the zoom ring is much more. The size and the weight are both quite acceptable, though not as compact as 18-55.
When it comes to image quality, let's start from the color. I can't find any significant difference between the Sigma and 18-55. The Sigma is a little bit more yellowish (or maybe more saturated?) while Pentax's green is greener, but it is not noticeable unless I switch between these two picture quickly, and a little more saturated isn't bad at all, is it?
Then about the most obvious difference: sharpness. This lens is very sharp throughout the field. The Sigma outperforms by far (easily distinguishable when displayed on 8' screen) the 18-55 at every focal length wide open (That is, Sigma F2.8 vs Pentax F3.5, or Sigma F3.5 vs Pentax F4, etc). Though 18-55 narrows the gap of center sharpness when both lens stopped down to F5.6 at 17mm or F8 at 28mm, the Sigma still leave 18-55 behind in edge sharpness.
The Sigma also has much less vignetting. Distortion is noticeable at wide angles, but not when zoom in.
The only flaw is auto-focus. My co... |
