UPDATED FEBRUARY 2017

When it comes to wide angle lenses, the field of view of a 24mm on a full frame sensor is both super popular and easy to shoot.  Once you go much wider, one has to pay a lot more attention to angles and perspective exaggerations.  On a crop sensor, a 24mm delivers pretty darn close to my opinion of the best "one lens prime" out there, the 35mm when on full frame.  In this review, we'll take a close look at Sigma's ART Series 24mm f/1.4

A 24mm is a terrific wide angle whether you shoot crop sensor or full frame.  Couple that lovely focal length with a very large maximum aperture and you have a killer lens option.

Let's start with mounting the 24mm on a crop sensor.  The Sigma comes in a variety of mounts and when on a Nikon say has the field of view of a 35mm and when on a Canon has the field of view of a 38mm.  If you are into, or want to get into, street style photography, this is a golden field of view.  It's not so wide that subjects look forty-two miles away, not so wide that if your sensor is not perfectly parallel, that your subject is leaning precipitously, but wide enough that you can get a really nice environmental story.  While I personally do not care for the sneak and shoot model of street photography, you can definitely get away with hipshots with this lens.

On full frame, the lens is less suited to street than to environmental, real estate and landscape work.  Again, the focal length is forgiving if you are not perfectly parallel to the subject with easily corrected lean should it happen.  When you do place properly and compose well, you can give a real sense of space and room, even in really tight quarters.  Real estate photographers in city centres love the 24mm because it allows them to make tiny rooms look larger without the telltale massive perspective exaggeration evidenced by a wider field of view.

In either sensor scenario, a 24mm is a very popular lens to use for night photography.  It offers a very wide expanse of sky and has enough field of view to reasonably include some land based foreground detail to give your night sky images a sense of scope and scale.

I also like a 24mm for sporting events, not for detail of the players, but for the environmental images so important to creating a story that pulls your images together in a slideshow or storyboard.  As a videographer, I find the fast 24mm very useful for interiors or to create expansive vistas, particularly as the light starts to wane.

The fast maximum aperture has numerous benefits.  It will allow you to shoot in very low light without supplemental light because of the enormous light gathering power.  There are nine aperture blades so out of focus highlights have a nice roundness to them.  I have read more than one blog post where the writer has challenged the blade count argument.  Sadly in every case, the full context was not understood by the writer and so he or she finds him or herself railing at lens design and the entire lens manufacturing community like Quixote challenging a windmill to battle.

 Because the 24mm is a relatively simple optical design, it can be made extremely sharp without a lot of excess weight.  The Sigma is a bit heavier than some of its competitors, not by faulty design but by tough materials in the construction.  The lens has minimal distortions natively with very minor barrel distortion easily corrected in any decent post processing application and nearly gone by f/2.8 regardless.  A 24mm has massive depth of field even at moderate apertures so one doesn't need to stop down to f/22 for everything.  While an argument will be made that not having to do so will limit the chromatic aberration (and it will), the more important question about whether you could actually see the aberration rarely gets asked.  In real world testing, you have to zoom in to the equivalent of a 30" print that you are observing from 6 inches away.  Thus irrelevant in all practical terms and only a useful conversation for those who would rather yap than shoot.

The rationale for the fast f/1.4 can only be driven by your personal use case.  If you aren't going to shoot this, or any, lens at f/1.4 on a regular basis, there is no really good reason to spend the extra money on the lens speed.  It is lovely to be sure, but if you don't use it, it makes as much sense as a Bugatti Veyron for a five minute commute entirely on residential streets.

I personally prefer very fast lenses, and if availed of one will tend to shoot it wide open a lot.  Yes you then get the narrowest depth of field, but it can also afford really high shutter speeds without bolting a rocket to the ISO when necessary.

Even when shooting wide open with this focal length, the depth of field is still decent when the subject is a short distance away.  As you can see in the table below, at a 10 foot subject distance at f/8, your depth of field runs from 4.41 feet to infinity.  

Thus even if you don't have a hyperfocal distance readout on your lens (now sadly gone from most lenses) set the focus manually to ten feet and your aperture to f/8 or smaller and street shoot without ever having to focus.  This is a very old fast shooters technique, but it has not been well articulated for digital and AF systems.  Please note that you are putting the camera / lens combination into manual focus mode.  

One of the other criteria one looks at in a very fast wide angle lens is how it handles flare from very bright sources.  In this sample image, you'll see that the Sigma 24/1.4 does a great job in this difficult lighting situation.

This was, as you can see, a really horrible lighting situation with the potential for lots of flare damage, ghosting, and really blocked up shadows. I shot three images at 2 stops apart and pulled them together in Aurora HDR Pro.  It's usefully illustrative because the image has the minimum depth of field possible at the focus distance and the greatest propensity for untenable flare out.  It still works out nicely and there is lots of detail in the shadows.  Perspective exaggeration is minimal and it is a pleasant enough scene.

The Sigma 24mm comes with a detachable hood and accepts 77mm filters.  Be careful if you use filters on this fellow because the field of view is so wide, many filters will intrude into the frame on a full frame camera producing vignetting.  If you must put a UV style filter on this lens, and many folks do, be CERTAIN that the one you get is a slim ring style.  B+W do excellent filters with narrow rings made of brass that do not bind and do not vignette.  Also be sure to ALWAYS use the hood.  That rounded front element as you see in the first image is a light collector and you want to ensure that stray light isn't depleting contrast and increasing glare.  Plus the hood offers you some useful front end protection.

I've written in other articles how excellent Sigma is when it comes to standing behind their products.  Where I reside in Canada, the factory warranty is 7 years.  Many photographers like to extend the manufacturer's warranty, especially when it's a skint one year offering.  At 7 years, you may not need to go with a warranty extension.  Canon offers one year and Nikon five years here in Canada, so the added peace of mind could be valuable to you.  

Speaking of the two largest competitors, here's an image courtesy of Sigma Rumors of the three comparable 24/1.4 lenses together.  The Sigma is plainly aligned with the excellent competition.

Where the Sigma lens stands out, is in the cost of acquisition.  As I write this, the Sigma is selling for $1099.00 CDN while the Nikon 24/1.4 is on sale at $2499.99 and the Canon 24/1.4 is on sale for $2089.99   Both the Canon and Nikon products are really excellent but it's not unreasonable to ask if your use cases warrant the price difference.  For a lot of shooters, the Sigma is a better choice overall, that decision is entirely your own.  I have shot all three and I cannot see any significant differences at normal viewing distances.

In conclusion, I really am impressed with this lens, the second of the Sigma ART series that I have evaluated.  When you take the cost into account, the return on investment is excellent and the image quality is also excellent.  There's nothing to lose here and the newer ART design and construction is definitely superb.  The only consideration is to ask yourself if you will shoot the lens wide open on a reasonably regular basis.  If yes, this is a great choice, but if you will only be shooting at f/2.8 or smaller apertures, save some money and buy an f/2.8 lens.  You may not get the same high level of construction but there's no point paying for something you won't use.  For my use cases, lens speed is always important so the Sigma would be a perfect choice.