Sigma APO 50-150mm F2.8 EX DC HSM Review

Over two month ago I tested this lens. It was very promising, specifitaions were intriguing. First impressions were really good. It was very well built, standard for Sigma's EX (excellence) class. The Sigma is a DC (Digital Camera) lens specifically designed for the reduced image circle of today's APS-C DSLRs where its field of view is equivalent to 80-240mm (I tested it with Canon 400D) on classic full frame SLRs. That's why it's quite a compact and light lens (770g). It has a constant f2.8 aperture (throughout the zoom range). Aperture has 9 diaphragm blades (which also contribute to a great bokeh). The HSM drive, Sigma's ultrasonic AF drive variant, is very fast and provides full time manual focus control. The zoom ring is quite "hard to turn" but it runs pretty smooth (no "jamming" etc), the manual focus ring is excellent. I guess I'm used to Canon's zoom rings, but this is normal for Sigma lenses (I've tested quite a few) Please note that the HSM drive is only available for Sigma, Canon and Nikon mounts. Minolta and Pentax users have to live with a standard micro motor which is surely somewhat slower. The lens does not extend during zooming and the front element remains in place so using a polarizer is no problem. Minimum focus distance is 100 cm, filter size is 67 mm.



Below you have the test samples. Unfortunately I hadn't had luck with the weather so most of the photos were taken at ISO 400 in the f2.8-f4 range (which will probably interest you the most anyway). 100% crops are ofcourse not postprocessed, resized images are sharpened (usually USM 50/1/4).


F2.8, 1/125, 77mm, ISO 400




F2.8, 1/250, 83mm, ISO 100





Below are two standard CA test shots. On the first simple ther's (almost) no visible CA, however on the second it's quite pronounced (please enlarge the photo by clicking on it).





Conclusion:
The lens is not as good as one would think when looking at specifications. Sharpness is very good from f4 above, especially towards the long end (100mm and more). CA can be pretty bad at f2.8. AF is fast and quiet, but this lens had a slihgt frontfocus issues. This is a serious issue with Sigma lenses, since 3 out of 8 lenses that i tested in the last 2 months had this issues. 5 of them were EX class, 3 of them had front focus issues, one of them a severe one (300 2.8). So it looks like, that you must have a lucky hand to pick one an EX (excellence) class Sigma lens, that focuses correctly. I suggest you try it before purchasing it.

Pros:
-sharpness at f4-f8
-fast and silnet AF
-price
-nice supplementation of the kit lens (which usually range from 17/18 to 50/55mm)

Cons:
-CA in some cases
-front focus of the tested lens
-sharpness at f2.8