Why this matters
Choosing a 35mm lens used to be easy for Canon shooters.  If you needed to freeze action, you bought the Canon 35 f/1.4L.  If you could afford to lose a stop, you bought the Canon 35 f/2L IS and saved a significant amount of money.  The 35 f/2 isn’t as fast as the 1.4L but you’d have IS.

Life couldn’t stay simple forever though;  the release of the Sigma 35 f/1.4 DG HSM complicated things.  It’s as fast as the 35L but doesn’t cost too much more than the 35 F/2 IS.  If you’re strictly looking for a 35mm f/1.4 the decision just isn’t clear anymore.  You may be thinking about the Sigma but let’s face it, it’s a Sigma and it is weighed down by the history of Sigma lenses.  Will it focus?  How durable is it?  What’s the image quality like?  Can it be as good as good a lens as the 35L?  On the other hand, is the Canon L that much better than you shouldn’t even look at the Sigma?

To answer these questions I pitted the Canon 35L against the Sigma 35 f/1.4 DG HSM and looked at their strengths and weaknesses to help others make the decision.

Construction
Both lenses are well-constructed and neither feels “cheap”, though the Canon’s construction feels more robust than the Sigma’s.  The Canon also has the magical L red ring that lets lets every photographer in the immediate vicinity know you’re sporting a “pro” lens.  It won’t make your photos any better, but they don’t know that.  Kidding aside, if your lens choice depends greatly on survivability, go with the Canon.  The build quality is what you’d expect from an L Lens: solid.  Another thing to factor-in here is Canon’s reputation for repairs vs. Sigma’s.  Sigma has made strides to improve service, but it’s hard to beat Canon’s factory repair (especially if you’re a Canon Professional Services member)

Notwithstanding, the Sigma 35 does not come across as a cheap second-rate lens as Sigmas tend to.  The lens is very well-made and its metal-plastic exterior with satin finish is well-executed.  It looks, and feels, like a high-end product.

Weight
The Canon 35L is the lighter of the two weighing in at 580g or 1.28lbs. The Sigma clocks in at 665g or 23.5oz.  I don’t think the weight difference is perceptible – though some may disagree.  I should note I was not aware of a weight difference until I looked up the specs for this review.

Weather Sealing
Neither lens is weather sealed. If this is important to you, you may want to take a look at the 16-35 f/2.8LII.  I encountered a couple of rainstorms during the testing period and I was frustrated by not being able to reach for the 35s.  Luckily the 24-105 f/4L is weather sealed and I was able to reach for that.

Image Quality & Sharpness
Wide open the Sigma is significantly sharper.  Take a look at the 100% RAW crop below (Canon left, Sigma right) and note the eye definition.  Both images were captured with a 5DMKII at ISO 800 and imported into Lightroom without any noise reduction or sharpening.

Canon-Sigma Side-by-Side Comparison at f/1.4

RAW comparison @ 100% at f1.4 Canon (left), Sigma (right)

The Sigma remains sharper until about f/2.8.  At this point, both lenses are almost identical.  In terms of vignetting, and chromatic aberrations, both lenses perform very well.  Chromatic aberrations are well-controlled and barely noticeable.  While vignetting is apparent at 1.4, it does subside (but does not completely disappear) at about f/2.8.  Speaking of aperture, the Canon’s minimum aperture is f/22 while the Sigma’s is f/16.

Focus
Focusing speed was similar and I didn’t note a difference between the two lenses.  I do think focus on both lenses is slower than typical Canon L lenses  (like the 24-105 f/4L or 70-200 2.8L).

The focus rings on both lenses have a nice weighty feel.  They’re both smooth enough to move but solid enough to prevent accidental movement.  I was worried about slack in the Sigma, but there was none to be found.

In terms of focus lock, while focus lock is largely driven by the camera’s autofocus system, I tested it nonetheless as there is always concern with 3rd party lenses.  Low-light focus was tested under two real-world conditions: a dark room similar to a wedding reception banquet hall and outdoors under dim city street lights.  I performed the tests twice making sure to use both lenses each time.  There was no difference between the two – neither hunted while the other locked.  Low-light focus should not be considered a factor when deciding between the two lenses.

Bokeh
35mm lenses are not the bokeh machines 85mm lenses are.  Nonetheless, one should have some idea of what bokeh is like when buying an f/1.4 lens.  Below are two images shot wide open.  As in the earlier comparison, the Canon is on the left while the Sigma is on the right.  I believe the Canon’s Bokeh is the creamier, smoother,  “butterier” (this shouldn’t be a word), (insert adjective here) of the two – especially in the shape of the “bokeh balls”.  Keep in mind, I wasn’t on a tripod here and the test wasn’t completely controlled, however, I did note that bokeh was more pleasing in the canon overall on multiple occasions.

The Gestalt aka: the “living with it test”
Both lenses are top performers, but the Sigma is markedly sharper.  When I wanted the shot, I reached for the Sigma.  In the end, it was that simple for me.  I liked the Canon L but I just couldn’t reach for it to shoot wide open.  That said, the Canon is no slouch especially at f/2.8 and up.  If you’re rough on your gear or are working in an environment where you need an a robust body the 35L is the way to go.

In the end, the Sigma 35 remained in my bag.  Below are  some of the recent shots I’ve taken with it.  It’s a fantastic performer that’s hard to match wide open.

Buy:
The Canon 35 f/1.4L and the Sigma 35 f/1.4 DG HSM are both currently available from B&H.

Rent:
 If you’re the type to try before you buy (or just want to double check this review), you can rent Canon 35 f/1.4L and the Sigma 35 f/1.4 DG HSM from BorrowLenses.com.