Yes, as everyone above has managed picked out, the left hand images were all from the primes, while the right hand images were all from the Sigma 17-50mm F2.8.
Originally posted by pcarfan The 50mm images on the left looks much better than the right side. So, I hope the focus is not off on the right side?
That was one result that I was quite surprised at. I didn't expect the quality difference to be that big, especially at F2.8, but then again, zoom lenses tend to not be their best at the very ends of their zoom ranges, and also, there may be focusing errors as you mentioned, or other issues at play.
Originally posted by Class A From this comparison, the differences (with a few exceptions) don't seem huge at all. Would be very interesting to see full images (not detail crops) in comparison as well to judge the bokeh.
At the 100% crops, three out of the three posters above managed to pick that the primes were on the left and the zooms were on the right, but I personally tend not to bother looking at 100% crops, so here are some comparison shots of the whole image. The photos are the full 18 or however much megapickels the K-5 is (MP isn't something I bother much about either) resized to 800px longest edge and then stitched. The results are a lot closer, pretty much with the exception of 50mm at F2.8 and maybe at F4.0:
Once again 35mm, and from top, F2.8, F4.0, F5.6 and F8.0, click for full size:
Then 50mm (with a red line to separate the columns of photos), from top, F2.8, F4.0, F5.6 and F8.0, click for full size:
My
personal thoughts are that at the end of the day, the Sigma 17-50mm F2.8 is a good lens, and
in general, there's not too much to differentiate today's top zoom lenses to prime lenses in most situations (i.e. non-pixel peeping); the versatility of a having a zoom range, as opposed to a fixed focal length is also much appreciated from my experience, especially for event photography. Having said that, prime lenses definitely do have their uses, and I'm yet to see a zoom lens that's faster than F2.8 for 35mm or APS-C (I know there's some F2.0 zooms for m4/3 though).