Originally posted by MikeD interesting according to the compare done on the Tamron, Pentax, and Sigma the Pentax came out 3rd in the IQ dept. Where is beat out the Tamron was in build quality and WR. With the Tamron having best center IQ and the Sigma being the best overall. The IQ of the Pentax was third overall compared to the Sigma and Tamron.
I know, I know - I just look at the photos, oddly enough. You're probably referring to this comparison on the forum:
Review: DA* 16-50mm vs. Sigma and Tamron 17-50mm F2.8 Comparison - Image Quality: Sharpness | PentaxForums.com Reviews Even there, if you look at the actual real-life ("field") photos (not test charts and brick walls), the Pentax gives better looking photos. I know I'm not the only one on the forum with this assessment. I would mostly compare the f/2.8, f/4, and f/5.6 examples, since that's where these lenses should generally be shot (between f/3.5 and f/5 or f/5.6 on the Pentax, and probably similar on the other lenses).
If you only care about mild advantages in sharpness, sure - choose another lens. But what about color and shadow detail? What about capturing and rendering the most information from the scene? They didn't test for that. Nor did they appear to account for it in the subjective evaluation, making it an inadequate review, IMO. I appreciate the review, and I'm not putting down the hard work that was done to write it. But I don't think it was possible for it to reach a fair and complete conclusion, because of these omissions. Fortunately, you can still judge for yourself by looking at the photos critically - you don't have to accept the review's stated conclusions.