Canon 24-70mm f2.8L vs Sigma f2.8 IF EX DG HSM
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On full frame cameras a 24-70mm lens is the standard zoom lens for most professional photographers whether you shoot weddings, portraits, journalism, sports, travel or landscape. A 24-70 f2.8 gives you a fast lens with a wide angle, normal and short telephoto capabilities. Almost every professional I know owns and relies on a 24-70mm lens.
For years I owned a Canon 24-70mm f2.8L lens and it was a workhorse lens for me especially for my photographs of dogs and kids and outdoor recreation.. I also used it for landscape photography (until I started using tilt-shift lenses). I sold my lens about two years ago anticipating that Canon would release a Mark II version of the lens that was image stabilized and a bit sharper and with less distortion at the wide end. To date (August 2011), that lens is not yet out. So for almost two years I lived without a 24-70mm lens, waiting for the new and improved Canon. In the meantime, Sigma lent me their 24-70mm f2.8 pro lens to test out. I borrowed Wayne Simpson’s Canon 24-70mm Canon and spent three days in the field shooting with the two lenses. Here is what I found out:
Canon 24-70mm f2.8L at B+H Photo = $1399.00 (weight 950g)
Sigma 24-70 f2.8 IF EX DG HSM = $899.00 (weight 790g)
As you can see from the photo above the Sigma lens is significantly smaller (and lighter) than the big Canon 24-70mm lens and the Sigma costs 40% less than the Canon lens. Can the smaller and less expensive Sigma lens hold its own in the field?
First a note on the design of the lens. The Canon lens physically gets larger when zoomed to 24mm and is shortest when zoomed to 70mm. This is a strange design feature because most lenses are physically longer at longer focal lengths like we see with the Sigma lens (see photos below).
At 24mm the Sigma lens is short and compact but the Canon lens is fully extended at 24mm.
At 70mm both lenses are the same size. Canon’s design means that the lens is larger and extends even longer at 24mm. This may seem counter-intuitive but it is actually kind of clever because the lens hood on the Canon then becomes fully functional at all focal lengths. The hood attaches to the lens body with a bayonet mount right above the red line on the lens. The hood is long and when the lens is extended to 24mm, only about 1/3rd of the hood is used. Pulled back to 70mm the full hood length is used. The Sigma lens has a short hood that is optimized for 24mm and when the lens is zoomed out, you still have a 24mm effective hood. So with the Canon you have a fully functional hood but with the Sigma it only works its best at 24mm.
So… the price you pay for the clever functional zoom within a long hood is that the Canon lens is bigger lens that weighs 20% more than the Sigma lens! If you do a lot of backlit photos then the Canon 24-70mm and its functional lens hood will better prevent flare.
A 24mm is a 24mm right?
Both the Canon and Sigma lenses are 24-70mm focal lengths so I expected both lenses to give me the exact same coverage when I swapped the lenses on the tripod-mounted body. I was surprised that with the camera in the exact same position that the two zooms gave very different angles of view at the same focal length!
What the heck??? How can the two lenses both zoomed to 24mm and mounted on the same camera body on a tripod (nothing was moved) give such different coverage? Is is because the Canon extends out at 24mm and so the front of the lens is closer to the subject?
If this is the case, then at 70mm when both lenses are physically the same size then we should see the angle of view be exactly the same. But both lenses produced different coverage even at 70mm even when the camera was fixed in position on a tripod. Note how Brando the dog is slightly larger in the frame with the Canon lens.
The Sigma gives wider angles of view than the Canon when both are set to the same focal lengths. Which one is more accurate is hard to say but for reference I tested both against my 24mm TS-E lens and the Sigma and the Canon 24mm TS-E had almost exactly the same coverage. I don’t think the Canon 24-70mm lens is truly a 24-70!
What About Close-Focus Abilities?
This one is easy, the Canon can focus significantly closer than the Sigma at both 24 and 70mm.
But which lens is sharper at close focus? Below is the same scene at the closest focus for each lens. The camera is tripod-mounted, live view, manual focus was used, mirror lock-up and an aperture of f8 was used.
Center sharpness (above 100% magnification in Photoshop) was similar at close focus at 70mm for the two lenses but with the nod going to the Canon 24mm F2.8L lens.
Edge sharpness at closest focus at f8 for both lenses was disappointing and both lenses suffered from fairly severe chromatic aberrations at closest focus at 70mm (see below).
What about Bokeh?
Bokeh is the the aesthetic quality of the blur in the out-of-focus areas. With fast lenses like a f2.8 zoom, the quality of the blur is important as a counter point to the sharp areas. To test how each lens rendered out-of-focus areas I shot various scenes at different focal lengths all at f2.8. Below are several sample photos. For me both the Sigma and the Canon seemed to render the out-of-focus with similar pleasing blur (but I give the nod to the Sigma for softer bokeh at 24mm).
I tested the sharpness of both lenses using my Canon EOS-1ds Mark III. I always use Live View and manual focus to test sharpness because auto-focus can vary with various lenses and each lens needs to be micro-adjusted for precision of focus. Live View with manual focusing gives consistent sharp results.
Both lenses are optimized for sharpness in the f2.8 to f8 range. Higher apertures like f11-f22 suffer from diffraction and yield less resolution than wider apertures. For example check out the 100% magnifications of the images below. The top photo is f2.8, the middle one is f8, the final one is f22. You can see that f8 is the sharpest, f2.8 next best and f22 trails far behind in sharpness. This was true for both lenses at all focal lengths.
At 24mm the Sigma performed better than the Canon at all apertures in both center and edge sharpness. Below are two samples the first center sharpness at f8 where there is only a minor difference between the two lenses and then edge sharpness at f8 where the Sigma does a better job.
In tests at 35mm, 50mm and 70mm, the Canon was slightly sharper in the center and at the edges of the frame than the Sigma but not by much. At f4 both lenses performed equally at all these focal lengths. From f5.6 to f22, the Sigma was sharper than the Canon at all of these focal lengths. As well, the Canon lenses produced darker photos than the Sigma lens even when both were shot at the exact same shutter speed and aperture. The Sigma photos were lighter and a bit more contrasty.
Overall I give the edge in sharpness to the Sigma lens which was a better performer at 24mm and as good or better than the Canon at all other focal lengths from f4 to f22. The Canon was better at f2.8 at 35, 50 and 70mm. If you are a landscape photographer the Sigma has less diffraction than the Canon at f16 and f22.
Below is a 100% magnified view of the scene above shot with the Sigma and Canon lens at 24mm and f22 — the Sigma lens handles diffraction at small aperture openings much better.
Both lenses were fast and responsive in auto-focus. I could get sharper photos with both lens using manual focus and 5x Live View, but auto-focus was pretty close in sharpness. I calibrated each lens using Lens Align and micro-focus adjustments in-camera and once calibrated each lens accurately popped into focus. Neither lens seemed better nor faster than the other when it came to action photography.
Both lenses produced images that looked similar. The Sigma lens produced slightly brighter and slightly more contrasty images than the Canon lens when both were shot in the same light at the same settings but overall both lenses produced crisp, sharp images.
The Canon lens has a filter size of 77mm which is common for Canon L lenses. The Sigma lens has an odd size filter thread of 82mm. If you use filters the odd size filter size on the Sigma might be a serious drawback requiring an investment in larger sized filters. For me, I use a Cokin Z-Pro Filter holder on my lenses and to get filters on the Sigma lenses was just a matter of buying an 82mm adapter ring for my filter holder. It would have been nice if the Sigma lens use 77mm threads which is a more common filter size than 82mm.
So Which One Should You Buy?
As always that depends. If you are a wedding or sports photographer who always shoots at f2.8 and likes to use back light, then I think the Canon is a good bet because it has better lens sharpness (by a small margin) at f2.8 and at all focal lengths except at 24mm. As well, the well designed lens hood/zoom mechanism on the Canon helps to prevent flare my having a more functional lens hood. Also the close focus ability of the Canon is better and sharper at 70mm than the Sigma lens and for detail photos at a wedding (rings, flowers, cake, tight face shots) this close-up capability would be welcome.
On the other hand, if you are looking for an all around travel and landscape lens, I would give the Sigma higher marks because it is smaller, lighter, sharper at 24mm and at all other focal lengths at apertures f4 and higher and it suffers less from diffraction at small f-stops (like f16 and f22). I also like that the 24mm setting on the Sigma is more true and more wide than the Canon 24mm setting. Also the Sigma lens is much less money which is always good. Both lenses seem to be robustly built and should handle the rigours of use well. Personally I prefer the mechanics and feel of the Sigma lens over the Canon lens.
For both the Canon and Sigma lenses I wish both manufacturers made a 24-70mm lens with image stabilization (optical stabilization for Sigma). Having a stabilized lens would really help photographers get the most of a fast f2.8 lens so that we can hand-hold at lower shutter speeds. Both lenses also suffer from chromatic aberrations at the edges of the frame and are not as sharp as they could be when focused close. I expect better performance from such high end pro lenses. Overall either lens is a fine tool that will serve most photographers well. Which one you choose, depends on your interests and budget. I have no idea whether Canon or Sigma plan to update these work horse lenses but it may be worth waiting to see if they do unless you just can’t wait. Either way, you’ll get great images with these two lenses but be aware of their shortcomings.
Note: I am sponsored by Sigma Canada and they provide me with lenses to use. I report things the way I see it and am not paid or influenced to bias the review. I use Sigma lenses whenever they perform better than Canon lenses. When they don’t I use Canon lenses. For my style of photography the Sigma 24-70mm lens is a better choice for me. Your mileage may vary.