Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- User Rating: 
Summary for Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- quality issues
Notes on Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- I returned the first lens because it was back-focusing with my Pentax K100D. The second lens was ok, but strangely, softer than the first one in tests with a focusing chart (albeit no backfocusing).
Both lenses appear softer than the Pentax kit 18-55mm, which is disappointing.
I decided to keep the lens as it is the only 17-70mm that works with K100D body, is not absolutely terrible, and is not very expensive.
If you buy this lens, check for backfocusing problems. Search the web for numerous posts about this.
Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- User Rating: Summary for Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- Sigma 17~70 DC Zoom for Pentax
Notes on Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- I purchased this lens to replace the standard kit lens that came with the Pentax K10D. It has proven to be of exceptional quality both optically and mechanically. I have shot it under many varied situations and it continues to give me the exact results I hoped for.
I plan to purchase the Sigma 70~300 APO MAcro zoom soon to supplement the 17~70 and expect the combo to fit 99% of my lens needs.
Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- User Rating: Summary for Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- Good quality Versatile Lens
Notes on Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- I purchased this lens for my Pentax K10D, and it works quite well. The zoom range is just right for most applications and the semi macro performance is handy. Performance wise it is very sharp, low CA, low vignetting and low distortions. At 17mm the performance sags a little with some distortion and when wide open some vignetting. In most cases I haven't had a problem. At 17mm, however, the distortion gets pronounced at distances less than 3 feet (1 meter), so take a few steps back if possible. Aluminum construction is nice.
Overall highly recommended!
Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- User Rating: Summary for Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- Defective?
Notes on Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- I used the 17-70 for a little over a week before coming to the conclusion that mine must be defective. Where other people rave about how it focuses on a dime even in low-light levels, mine could barely be persuaded to focus on the best of days in perfect light. Very few of my pictures taken with it were what you could call crisp and none "tack sharp." Plus, it's very heavy, which made it difficult for me to handhold w/o some motion blur which only added to my problems. My father owns this lens and swears by it and his pictures ARE tack sharp with no vignetting or chromatic aberrations, so that was ultimately what lead me to conclude it defective. I returned it to 47th Street Photo, who still have yet to give me my refund, despite having had the lens since the 11th of january, and even though there will be no re-stocking as they will be sending it back to the manufacturer, they are charging me an exorbitant $50 "re-stocking" fee as I decided I didn't want another one of these behemoth lenses in my camera bag.
Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- User Rating: Summary for Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- Nice walk around lens, excellent color
Notes on Sigma 17-70mm f/2.8-4.5 DC IF Macro Lens ...- I got this lens about a month ago and it has been on my Pentax K10D for most of the time. The lens produces sharp pictures with nice colour and contrast in daylight and covers a good range from wide angle to medium telephoto. The only issue is that f2.8 is only available till 21 mm. Not the best choice if you want to shoot in low light.
