Like many DSLR users with a current generation 6MP camera, I have severely missed having a true wide angle lens.  Today’s 6MP DSLR cameras with their APS sized sensors and 1.5 – 1.6 magnification factors make most wide angle lenses only mildly wide at best. About six months ago I bought a Canon 17-40 f4 L in the hopes to fill my need for a true wide angle lens. Unfortunately, the 27-64mm lens that it turns into on a cropped sensor DSLR is not very wide, leaving me regularly wishing for something wider. With the announcement of Sigma’s 12-24mm f4.5-5.6 EX DG HSM I had renewed hope of having a truly wide angle lens for my DSLR. I recently purchased the Sigma 12-24mm hoping to replace my Canon 17-40 f4 L with it. I figured that I would test both lenses at their equivalent focal lengths (17 and 24mm) to see how well they compared. If their performance was similar I would keep the Sigma because it offers much wider angles (19-38mm) compared to the Canon. Below are my impressions of how the two lenses compare. All comparison were made based on photos (see bottom of page) that were taking with a tripod mounted camera that was not moved during lens changes. All comparison photos where taken within minutes of each other so the light was the same. Please note that I am not a professional camera equipment reviewer and I did this comparison/review to meet my own needs. Therefore the techniques and methodology that I used may not be ideal. However, I think my results are informative and may be helpful to a lot of other people, especially if you are trying to pick between these two lenses. So please take what you will from my review but also take my results with a grain of salt and verify your own lenses.

 

Initial Impressions:

This Sigma lens is BIG. Much bigger and heavier than the Canon 17-40 (see photo). I have heard others refer to this lens as Popeye for very good reason. The front lens element sticks out a substantial amount giving the lens an unusual look.

 

Build Quality:

To my surprise, the Sigma’s build quality is much better than I expected. Zoom and focus rings are smooth and well damped. HSM is very quiet and compares well overall to Canon’s USM, however I think USM is slightly faster. Overall build quality is very good. If I were to rank my lenses on overall build quality I would definitely have to give my Canon L lenses first place (I also have a Canon 70-200 f4 L), the Sigma would get second and my Tamron 28-75mm XR Di f2.8 would get a distant third.

                                         

Optical Quality:

Opitcal Distortion – Pincushion and barrel distortion are very well controlled on the Sigma 12-24. Straight lines look almost perfectly straight at all focal lengths. The Sigma’s performance is definitely top notch in this area, handily beating the Canon 17-40. For architecture photography this lens stands alone as probably one of the best wide angle lenses currently available. However, it should be noted that round objects do sometimes get distorted (egg shaped) due to the extreme angles. 

 

Color, Contrast and Lens Flare –  Color seems very good overall and compares well to the Canon 17-40. Contrast on the other hand does not seem as good. Photos with the Canon 17-40 almost always seem to have darker more defined differences between light and dark areas. There may not be a huge difference between lenses, but there is enough for me to think that Canon is better. Compare the samples to decide for yourself. The Sigma definitely seems more susceptible to lens flare. However, this can be minimized through good technique and shading the lens when possible so it is not a deal breaker.

 

Sharpness – Here is the subject that I think is by far the most important for a lens (at least to me). Unfortunately, this is where the Sigma falls apart. I had two Sigma 12- 24 lenses over about a month due to that I thought the first lens was defective due to some very soft areas. The second lens was slightly better overall, but still had very soft areas. With the first lens the soft areas were spread unevenly across the outer edges of the lens. With the second lens the softest areas seem to be on the right and bottom with the bottom right corner being the worst. The samples I am providing are based off the second lens since I think it is the better of the two. Unfortunately, it was still a disappointing showing by the Sigma. When compared to the Canon at 17mm and 24mm the Canon truly shows its superiority. The Canon is usually sharp edge to edge by f5.6 and very sharp by f8. f4 on the Canon was a little soft overall, but was still very usable. By contrast, the Sigma was always soft in the newspaper shots on the right and bottom no matter what f-stop was used. At f16 the Sigma looked better, but never sharp in the newspaper test. In real world outdoor shots the Sigma did better depending on the focal length and aperture used. At low apertures the Sigma was always much softer than the Canon. At higher apertures of around f16 at 17mm, the Sigma compared very well to the Canon. At 24mm the Sigma was always softer.  The Sigma also shows similar results at 12mm, for obvious reasons I do not have a comparable Canon photo. Because both Sigma’s had very soft areas, but the soft areas were in different areas on each lens, I have to seriously question Sigma’s quality control. I have considered exchanging my lens for a third lens to see if the third one would be the charm. It seems possible that there may be some flawless copies of this lens available. Finding one seems to be the challenge that I am not sure is worth the effort.

 

Conclusion:

Overall, I would have to say that I am disappointed in the Sigma 12-24. As much as I want a true wide angle lens for my DSLR, I am afraid I will pass on the Sigma 12-24. The softness is a little too severe for my tastes. That being said, it is still possible to get some great photos with this lens (Please see the following examples Zion NP 1, Zion NP 2 ) and it does have very low optical distortion making it good for architecture photography. If money were no object I would keep the Sigma for when I need something wider than 17mm. Unfortunately, money is a precious commodity and I have to choose between the Canon 17-40 f4 L and Sigma 12-24. Due to the Canon’s superior sharpness and contrast it is no contest to me. If you decide to give the Sigma a try I would suggest testing it thoroughly. As I stated before, I think it is possible there are some good copies of this lens out there. I just did not get one on my two attempts.

 

If I were to rank my current lens and ones I have recently tested from best to worst I would rank them like this;

1.      Canon 70-200mm f4 L - Very sharp with good contrast at all focal lengths and apertures. Excellent build quality.

2.      Tamron 28-75mm XR Di f2.8 - Very sharp with good contrast from f4 and higher. Does not have the equivalent of USM or HSM and build quality feels a little cheap, however the price is very low.

3.      Canon 17-40 f4 L - Very sharp with good contrast from f5.6 / f8 and higher, not as sharp as the Tamron at the same focal lengths. Excellent build quality. A very close third.

4.      Sigma 12-24mm f4.5-5.6 EX DG HSM - Very wide lens that currently has little completion (none with Canon cameras). Low optical distortion making it good for architecture. Soft along edges and in corners on cropped sensor DSLR’s. On a full frame SLR/DSLR I would expect softness to be much worse. Good build quality if you don’t count varying softness problems from one lens to the next.