Thanks for the comments on this lens. What is coma? It would be nice to see a couple of shots posted. Really nice would be comaparisons with the Pentax 16-45mm :-)
Jens Bladt mailto:[EMAIL PROTECTED] http://hjem.get2net.dk/bladt -----Oprindelig meddelelse----- Fra: Frantisek [mailto:[EMAIL PROTECTED] Sendt: 28. november 2004 23:44 Til: PDML Emne: Sigma 2.8/18-50 DC first impressions Hi, As I promised, I will write some first impressions of this lens. Later, when time permits, I might post few crops from the sample I tried. Keep in mind that this is preliminary, based on just quick'n'dirty evaluation of just few test photographs. Real "review" would be based on using the lens to actually photograph some more real world subjects than a backyard scene from the balcony of the photographic shop (although the scene was varied nicely in contrast and detail). Long end - good overall, low vignetting, slight coma in the outer zones. Contrast is good. Overall, the lens is very respectable at 50mm and 2.8 aperture. Best performance is at f/8, but even at f/4 you would be hard pressed to find faults and 5.6 is almost indistinguishable from f/8. I couldn't see any big chromatic aberration which was a plus. Wide end - quite visible coma in 2/3 and outer zones of the reduced frame plus overall veil make the image soft at full aperture (although not nearly as much as Sigma's previous 1.8/20mm lens was at 1.8). Coma is decreased somewhat at f/4, and virtually gone by 5.6. Veiling is virtually gone by f/4. No big visible chromatic aberration! Vignetting is severe at 2.8, slight but still somewhat noticeable at f/4 and virtually gone by 5.6. Overall, wide open the performance is just acceptable (but I have seen worse). Once stopped to f/4 it gets much better, with 5.6 and 8 being both very good. Finer details of the lens (tonality, boke', et cetera) would require having it for much longer. I am still somewhat at a loss about the wide end wide open pictures. Some of them looked good, and some looked bad. Will have to try it more. For the money, it doesn't seem as a bad lens at all, with good wide open performance for portraits but questionable wide open 18mm end. The inevitable comparison would be to 16-40 Pentax. Which I don't have ;-). The 1 stop gain is real (unlike some older Sigma lenses like the EX 1.8/20mm which had true T/stop around 2.2-2.3 and were unusable until 2.80), and usable at the long end, but at the wide end, for good performance you have to stop down to f/4 anyway... Frantisek
