Wednesday, April 22, 2015

Sigma 24mm 1.4 DG HSM Art Review

Sigma 24mm 1.4 DG HSM Art


This is the Sigma 24mm 1.4 DG HSM ART lens. It costs less than the equivalent Nikon or Canon, and is just as or is nearly as good. For many people, that is enough to know....

Build and Construction


If you aren't familiar with the new Global Vision Sigma lenses, the casing is made from a composite material that has an appearance midway between being metallic and glass-like. The overall impression of the flat gloss finish is upscale and arguably more attractive than what either Canon or Nikon package their lenses in. This is not merely made with a conventional plastic,and instead uses a type of composite material that Sigma has branded TSC(TM), for "Thermally Stable Composite." This is a polycarbonate-based composite. The key benefit of the material appears to be that it has similar thermal expansion properties as metal, meaning that the lens as a whole can be built to smaller tolerances. The interfaces between the plastic parts of the lens and the metal parts can be made smaller, thus reducing size and weight. That said, this is neither a light nor a small lens. It will be at home on a Canon 5D Mark III or a D810, but it will feel distinctly front heavy if you use it as a mid-wide lens on a smaller camera like the D7200 or the EOS 7D Mark II.

Like it's 35mm brother, the focus ring is a wide flat band that is easy to grab a hold of, and has a large degree of fluid damping for precision manual focusing. Focus is quick and quite in much the same way that Nikon's AF-S or Canon's USM lenses work. The front filter size is 77mm, which is not uncommon, but which puts it firmly into the category of "big and expensive" like. There will be two schools of thought about filters and good quality lenses. The first would be that since you would be using this lens to grab the utmost in terms of sharpness and resolution, a protective filter would be antithetical to its purpose. The second school of thought goes along the line of: "It's a $1000 lens..." That depends on comfort level; for some people that is dear amount of money, for others it isn't. However, be warned that to match the optical level of this lens, you would need the highest quality, something on the order of a B+W 77mm XS-Pro UV MRC-Nano  or the Hoya 72 mm Pro1 Digital MC UV-0. Filters at this size and of this quality don't come cheap if you don't shop carefully.


The 24mm is like the 35mm and the 50mm ART lenses; certainly, it's a prime, but it's not small. Even on a mid-size full frame camera like the Nikon D750 or Canon 6D, the overall package is weighty. It's just enough to carry around as a walk-around lens, but just barely. That is in keeping with the stated mission purposes of what an "ART" lens is; optical quality first, size compromises second.


Optical Quality


Of course, the optical quality is good. For the price it's fantastic, actually. Here is what 24mm looks like, as used on a Nikon D750:


Low geometric distortion and vignetting 

There is a small amount of barrel distortion, but not enough to be intrusive if the scene lacks dominant horizontal and/or vertical lines. Vignetting is in keeping with what you would expect for a fast wide prime; best results when stopping down. Chromatic aberration is very well controlled. Peak resolution occurs roughly between f/4 and f/5.6, but contrast is already fairly high at f/1.4. Just like the other ART lenses, the 24mm is one that you will have few reservations using wide-open.

Though there are many aspects to quantify (resolving power, field curvature, distortion, aberrations, etc.), a general sense of a lens’ character can be determined without resorting to lab testing. The following is one aspect; bokeh and apparent background blur with the subject at short distances.  First, here is the overall scene, shot at f/1.4:


f/1.4


The Lego Ralph Wiggum figure is approximately two feet away from the camera. Two subjective things jump out immediately. The first is that yes, there is bokeh at this wide angle of view. It doesn't obliterate the background, but it does provide separation between the foreground and background. The second is that the amount of vignetting is quite prominent along the edges. (Just as a reminder, the Nikon in-camera JPEG vignetting correction only works with Nikon lenses.) The following is a series of center crops, in comparison to the Nikon AF-S NIKKOR 24-70mm f/2.8G ED

Sigma 24mm ART at f/1.4 and f/2
f/2.8

f/4

f/5.6
f/8
For most people, the 24-70 f/2.8 is already an impressive lens. The bokeh quality between the two from f/2.8 upwards isn't meaningfully different in this sample set. Note that the Nikon is giving a slight bit more magnification even though the nominal focal length is the same between the two lenses. The center contrast on the Sigma is heavier than the Nikon at f/2.8; the colour saturation is just a smidge higher and the difference between the yellow skin and brown pants is slightly more pronounced. By f/5.6, there isn't much difference, if any.

Here's a standard super market shot of tomatoes on the vine. As you can see in the background, bokeh highlights aren't perfectly round at the edge of the frame. Nevertheless, the quality of the bokeh is not unsettling, which can be a danger if you combine a sharp fast lens with a busy background.


f/1.4

Shallow depth of field and wide-angle lenses don't exist easily together in average shooting conditions, so naturally, the main draw of a f/1.4 aperture on a wide-angle lens is the ability to shoot in lower light situations. While this is true, its not always ideal. If the quality of the light is flat and uninteresting the end result will also lack punch, regardless of what aperture you shoot in. Being able to shoot at a wider aperture helped to get the shot of this flower arrangement, but it couldn't do anything about the dull flat ambient light.

f/2.2
In good quality light the Sigma not only produces high amounts of detail, it has a strikingly contrasty rendition. All of the ART primes share this quality; even as focus rolls off into the background out-of focus areas, contrast stays hig, giving the global impression of sharpness even with shallow depth of field scenes like the pineapple display below

f/1.4
You might have noticed a re-occurring them with this set of sample images. Yes, they are all taken at an extreme close-up position. That's partly to illustrate the "bokeh"  a fast aperture wide-angle can produce; this is why you are interested in this lens right? The depth of field effect decreases considerable as the subject is placed further from the camera. However, another reason for choosing close angle shots is to illustrate the compositional challenge of wide-angle lenses in particular. At 24mm and wider it's a challenge to find something to anchor the eye to in order to create an interesting image. It's not just about getting more into the image, it's about managing the extra amount of depth.

f/1.4

Though there are wider alternatives, 24mm is the traditional boundary between "wide" and "ultra-wide." Though many zoom lenses cover 24mm (24-70mm, 16-35mm etc) there is a case for having a dedicated 24mm lens, as it does have create a palpable sense of drama without going overboard.  For some people, 28mm is the "weak sauce" version of the 24mm field of view; for most, 20mm is wide enough that it draws attention to itself rather than to the subject.

Concluding Thoughts



Left to right: 24mm, 35mm and 50mm Sigma f/1.4 ART lenses

This is very obviously a lens for full frame cameras. You could use it for crop frame as a 35mm "street photography" equivalent, but the size, weight and cost of the lens would be a mismatch for a crop frame body. Like the 35mm and 50mm Art lenses, the price isn't so extreme that it's not unimaginable for the average user. As far as pricing goes, it's a non-contest. By the mere fact that the Sigma is hundreds of dollars less than the Nikon and Canon equivalents it is a serious contender; because it is almost the same or better in terms of optical quality makes it hard to ignore.

This pricing strategy is quickly becoming the norm in the camera industry, to place lenses in the $800-$1000 USD range. This is pushing the price point up from what enthusiasts were used to in the earlier days of the digital SLR age, but it's not as exorbitant as what the high-end red and gold ring lenses cost. Have a look around at how many quality lenses are being introduced at that price point: The Sony 55m f/1.8 for A7r, many of Fujifilm's lenses, and now Sigma, with the 24mm, 35mm, 50mm and all falling within the $900-$1100 range. This isn't coincidence; its a competitive strategy against Nikon and Canon, who traditionally produce lenses at the high end above the $1500 mark.

As a means of drawing customers away from Canon/Nikon, Sigma and the other camera system manufacturers seem to be standardizing around the $800-$1200 price point because it is still somewhat affordable, but more importantly, it makes shopping easier. If this trends persists, it will make decision making a no-brainer for customers; no matter what lens you have now, your next lens will cost approximately $1000 USD regardless of what you chose. The best way to sum up the Sigma 24mm ART is to use the same concluding thought for the well-received 50mm:

"... We are making a big deal of the performance of this lens, but there's a good chance that many future lenses will be like this, and one day this level of performance will be "normal."

As far as norms go, expectations of this level of quality is now normal for Sigma.




With thanks to Broadway Camera

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