At first this may seem like an odd comparison, but the more I think about it the harder this choice becomes. Besides the obvious of the 18-35 being crop-only and the 35 being a prime and slightly faster, what are the justifications of a crop shooter to choose the 35 over the 18-35 when you can set the 18-35 @ 35mm and use it there when you need it?
I've heard both lenses be described as "game-changers" and its not hard to be excited over them. They are both built well, are reasonably priced, and deliver great sharpness without the AF issues that plagued the older Sigma primes.
This is what some publications have to say about this:
NOTE- all titles are links to the actual review
DPREVIEW
The Sigma 35mm F1.4 DG HSM impressed us hugely when we reviewed it at the end of last year, and is probably the sharpest 35mm F1.4 prime on the market. When tested on the same camera, the zoom may be just fractionally less sharp at large apertures, but you probably wouldn't see any difference in real world shooting. The zoom also has slightly higher vignetting and distortion, but lower chromatic aberration. From this data, you'd be hard pushed to see any meaningful differences between the two in side-by-side shooting. Remember this is the 18-35mm's weakest focal length.
Our final comparison, ironically, has the new Sigma up against the firm’s new 35mm f/1.4 DG HSM A, the best performing full-frame 35mm lens in our database. Although it’s easier to make a high-speed 35mm than either a 24mm f/1.4 or a 18mm f/3.5, the Sigma 35mm is without doubt a superb performer optically and yet the new Sigma 18-35mm zoom comfortably achieves a higher DxOMark Score. The new zoom also has slightly higher levels of sharpness and has the edge in uniformity. Less important perhaps is the superior transmission score, while the differences between distortion, vignetting and chromatic aberration are practically negligible.
I tested the sharpness of this lens in a number of situations, and found it to be pretty consistent and sharp at all focal lengths and apertures. Yes, it is most certainly sharpest between f/5.6 and f/7.1, with the best image quality at a wide angle produced at f/2.8. However, it still performs pretty well at f/1.8, just maybe not quite as good as many of us were hoping. It certainly is softer than the 35mm f/1.4, but is markedly better than any other variable focal length kit lens in this range that I have used.
Compared to Primes and Zooms
As we already hinted a little bit, it’s hard to compare this lens to others because it goes in a completely new direction. While you might be tempted to compare the 18-35mm to “regular” 17-55mm f/2.8 mid-range zooms on a crop-sensor, in my opinion the Sigma compares better with primes. And as such, there simply is no single lens on the market that can compare; really you should be comparing the Sigma 18-35 against 2-3 primes. This introduces a whole can of worms- Firstly, there simply is no 18mm f/1.8 crop-sensor prime available. There’s the Sigma 20mm f/1.8, but it is pretty old and quite soft wide open. Next, the Canon / Nikon 24mm f/1.4‘s are very pricey full-frame lenses, so they are once again not very practical for a crop sensor shooter. Thus, we are left with 28mm f/1.8 primes (both Canon and Nikon make them) …and of course the 35mm f/1.8 and f/1.4 primes that are made specifically for crop-sensors. (Nikon and Sigma make some)
In this light, the Sigma 18-35 f/1.8 makes a whole lot of sense. I work as a wedding photojournalist, and as far as mid-range lenses are concerned I would definitely rather have this Sigma 18-35 f/1.8 plus a more versatile zoom like the Nikon 16-85, instead of a single f/1.4 prime and a 17-55mm f/2.8 zoom.
If you’re having trouble wrapping your head around this whole comparison, just remember: Barely ~10-15 years ago people were having this very same discussion about f/2.8 zooms versus f/2.8 primes- f/2.8 zooms were finally becoming sharp enough that f/2.8 primes were becoming obsolete. Just some food for thought.
Compared to Full-Frame Options
Sure, there are pretty slim pickings for crop-sensor primes, and if you’re planning on sticking with crop-sensor cameras then the Sigma will be reigning champion for many years to come.
However, what about simply comparing the Sigma 18-35 f/1.8 against, say, a full-frame camera and 2-3 primes, or an f/2.8 zoom? The DOF (depth of field, aka background blur) on an f/2.8 zoom on full-frame is about the same as the DOF of an f/1.8 zoom on a crop-sensor. And of course if you throw an f/1.8 or f/1.4 prime on full-frame, you’re certainly going to achieve more shallow DOF and better low-light performance overall.
At this point, the comparison becomes even more difficult. In my opinion however it is not fair to simply compare a single full-frame camera with one lens, and a single crop-sensor camera with one lens. You need to compare the systems as a whole.
Indeed, the Sigma 18-35mm f/1.8 at $799 is not cheap, and you can probably buy 2-3 equivalent full-frame primes for the same price- Nikon’s 28mm f/1.8 G and 50mm f/1.8 G would set you back about $800, for example, if you took advantage of one of Nikon’s common rebates.
However what most “FF fanboys” fail to do is, compare the entire system and overall long-term costs. And that way, any way you slice it, full-frame becomes more expensive than crop-sensors by $1,000-$3,000 or more.
The bottom line, to me, is that sensor technology has improved quite a lot over the past few years, and nowadays a crop sensor is really all I need for a lot of the casual / outdoor photography that I do. And with every year that passes, I become less interested in what setup is the absolute champion on paper, and more excited about which setup is smaller, lighter, affordable, and yet still sharp and detailed enough to make big prints.
As we already hinted a little bit, it’s hard to compare this lens to others because it goes in a completely new direction. While you might be tempted to compare the 18-35mm to “regular” 17-55mm f/2.8 mid-range zooms on a crop-sensor, in my opinion the Sigma compares better with primes. And as such, there simply is no single lens on the market that can compare; really you should be comparing the Sigma 18-35 against 2-3 primes. This introduces a whole can of worms- Firstly, there simply is no 18mm f/1.8 crop-sensor prime available. There’s the Sigma 20mm f/1.8, but it is pretty old and quite soft wide open. Next, the Canon / Nikon 24mm f/1.4‘s are very pricey full-frame lenses, so they are once again not very practical for a crop sensor shooter. Thus, we are left with 28mm f/1.8 primes (both Canon and Nikon make them) …and of course the 35mm f/1.8 and f/1.4 primes that are made specifically for crop-sensors. (Nikon and Sigma make some)
In this light, the Sigma 18-35 f/1.8 makes a whole lot of sense. I work as a wedding photojournalist, and as far as mid-range lenses are concerned I would definitely rather have this Sigma 18-35 f/1.8 plus a more versatile zoom like the Nikon 16-85, instead of a single f/1.4 prime and a 17-55mm f/2.8 zoom.
If you’re having trouble wrapping your head around this whole comparison, just remember: Barely ~10-15 years ago people were having this very same discussion about f/2.8 zooms versus f/2.8 primes- f/2.8 zooms were finally becoming sharp enough that f/2.8 primes were becoming obsolete. Just some food for thought.
Compared to Full-Frame Options
Sure, there are pretty slim pickings for crop-sensor primes, and if you’re planning on sticking with crop-sensor cameras then the Sigma will be reigning champion for many years to come.
However, what about simply comparing the Sigma 18-35 f/1.8 against, say, a full-frame camera and 2-3 primes, or an f/2.8 zoom? The DOF (depth of field, aka background blur) on an f/2.8 zoom on full-frame is about the same as the DOF of an f/1.8 zoom on a crop-sensor. And of course if you throw an f/1.8 or f/1.4 prime on full-frame, you’re certainly going to achieve more shallow DOF and better low-light performance overall.
At this point, the comparison becomes even more difficult. In my opinion however it is not fair to simply compare a single full-frame camera with one lens, and a single crop-sensor camera with one lens. You need to compare the systems as a whole.
Indeed, the Sigma 18-35mm f/1.8 at $799 is not cheap, and you can probably buy 2-3 equivalent full-frame primes for the same price- Nikon’s 28mm f/1.8 G and 50mm f/1.8 G would set you back about $800, for example, if you took advantage of one of Nikon’s common rebates.
However what most “FF fanboys” fail to do is, compare the entire system and overall long-term costs. And that way, any way you slice it, full-frame becomes more expensive than crop-sensors by $1,000-$3,000 or more.
The bottom line, to me, is that sensor technology has improved quite a lot over the past few years, and nowadays a crop sensor is really all I need for a lot of the casual / outdoor photography that I do. And with every year that passes, I become less interested in what setup is the absolute champion on paper, and more excited about which setup is smaller, lighter, affordable, and yet still sharp and detailed enough to make big prints.
The big question is ‘Should I Buy This’ and that is somewhat of a tough question. Is it worth it? Absolutely the Sigma 18-35mm f1.8 is worth every penny bringing top of the line build quality, amazingly wide apertures, zoom abilities, and fast autofocus for only $799. However, this is not quite ‘cheap’, especially for an APS-C camera and the zoom range is somewhat limited. If you were considering the Sigma 35mm f/1.4, 30mm 1.4, or a Canon/Nikon alternative, I would seriously consider the Sigma 18-35 as the flexible range more than makes up for the lost 2/3 stops of aperture. Also, if you find yourself shooting indoors in tight spaces and frequently use this focal range, the Sigma should be your top choice. While there are some compromises with the large size and somewhat limited range for a zoom lens, the Sigma 35mm f/1.8 HSM lens [sic- should be 18-35mm I believe] is by far one of the most amazing zoom lenses around.
THE-DIGITAL-PICTURE
The comparison tools weren't perfect (different camera sensor, no 1.8 test setting for the 35mm prime), but from the looks of it, the 35 prime is alot sharper in the center near wide-open with the corners looking similar:
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Regardless of what conclusion we draw from this, it seems this is a great problem to have- who can't wait for more exciting gear? I sure can't.
Oh, and one more quote for people who in my boat:
LearningCameras 2013-07-21 00:08
I used to own the Sigma 17-50mm as well before I upgraded to full frame. The Sigma 18-35 is for sure a big upgrade. It is sharper, has faster AF, quieter AF, and has build quality of a pro end lens. However it is not stabilized so that is something to consider but it does have more than 1 stop wider aperture which is huge.
