In what is a very interesting and a revolutionary move in many ways, Sigma announced today their new 18-35mm F/1.8 DC HSM zoom, part of their new "Art" series of lenses. This super-fast constant aperture zoom covers an APS-C sensor only and with its 79x122 mm and 810 gr. is small, compact and light enough for the fast aperture it provides. As a reference for comparison, its filter size is just 72mm, not the usual 77mm that constant f/2.8 zooms generally use.
The new Sigma's main head-turning specification is its aperture: an constant aperture of f/1.8 on a zoom lens is a world-first, and a very impressive engineering achievement! On an APS-C camera, f/1.8 provides the same depth of field control of a f/2.7 aperture on full-frame DSLR cameras; however, the lens' f-stop is still f/1.8, so the new 18-35 allows you to shoot with shutter speeds about 2 stop faster (1 1/3 stop faster, to be precise) than, i.e., a 24-70 mm f/2.8 zoom on full-frame at equivalent light levels and ISO. What is most important, this lens opens new creative possibilities previously unavailable not only to APS-C users, but to any photographer in general in terms of shooting in low light, while at the same time bringing APS-C users the same level of depth of field control that full-frame users enjoyed with their f/2.8 zooms. On paper, the lens is very very good: very sharp across much of the frame already at f/1.8, with very low and simple distortion and vignetting (see full lens data HERE). Of course real world performance, which is what counts, has yet to be seen; however, it is a very impressive achievement for Sigma and one they need to be applauded for, both in general and in particular for the reasons below (keep reading after the break).
The new Sigma's main head-turning specification is its aperture: an constant aperture of f/1.8 on a zoom lens is a world-first, and a very impressive engineering achievement! On an APS-C camera, f/1.8 provides the same depth of field control of a f/2.7 aperture on full-frame DSLR cameras; however, the lens' f-stop is still f/1.8, so the new 18-35 allows you to shoot with shutter speeds about 2 stop faster (1 1/3 stop faster, to be precise) than, i.e., a 24-70 mm f/2.8 zoom on full-frame at equivalent light levels and ISO. What is most important, this lens opens new creative possibilities previously unavailable not only to APS-C users, but to any photographer in general in terms of shooting in low light, while at the same time bringing APS-C users the same level of depth of field control that full-frame users enjoyed with their f/2.8 zooms. On paper, the lens is very very good: very sharp across much of the frame already at f/1.8, with very low and simple distortion and vignetting (see full lens data HERE). Of course real world performance, which is what counts, has yet to be seen; however, it is a very impressive achievement for Sigma and one they need to be applauded for, both in general and in particular for the reasons below (keep reading after the break).
A quick bit of history. APS-C, providing a crop factor of 1.5x compared to what used to be the classic 35mm negative size or full-frame in modern camera talks (FF, 24x36mm sensor size), is the format manufacturer used at the beginning of the digital revolution basically for cost containing and ease of production in sensor manufacturing. Since then, Nikon, Canon and Sony eventually went on producing FF cameras, while keeping APS-C cameras in their line-up. Other manufacturer, like Olympus and Panasonic, went the other way from the start and developed 4/3 and micro 4/3 camera, with a crop factor of 2x compared to FF, to profit from the reduction in size and weight that this could bring.
This would all be fine per se. The problem, however, is with the lenses.
What does this mean? In short and to keep it simple: with the 1.5x crop factor, tele-lenses users are very happy (a 300 mm f/2.8 suddenly gained the field of view of a 450 f/2.8, and gained a bit of depth of field, too), while wide-angle (WA) users are not so happy (their 17-35 mm f/2.8 suddenly became a 27-50 mm f/2.8 FOV, loosing some depth-of-field control in the process too).
Coming to prime lenses, the old primes work just fine after the 1.5x crop factor, but focal length spacing suffers a bit. 28, 35, 50, 85, 105, 135, 180, 200, 300, 400, 500, 600 mm lenses now offer a field-of-view (FOV) equivalent to that of 42, 52, 75, 127, 157, 202, 270, 300, 450, 600, 750, 900 mm lenses. As you can see, a gain in tele, a lost in WA and a strange, new equivalent field of view spacing to get used to.
What did the big manufacturers do to fix the lack of APS-C WA primes and WA & WA-to-normal zoom lenses? What did they do to "fix" the FOV and focal length spacing for APS-C users? And more important, what did they do for their professional APS-C users?
Basically, very little, very late. They practically didn't produce any primes in the WA and Ultra-WA range except for fish-eye lenses. Coming to zooms, besides a plethora of 18-xx APS-C consumer zooms, generally f/4.5-f/5.6 or similar, we saw the appearance of more "serious" lenses in the 17 to 50-55 mm range with fixed apertures of f/2.8 first, and later of lenses in the 11-12 to 24 mm range with fixed apertures around f/4. While some of them were quite good, these lenses either provided less speed for comparable FOV in FF, or they offered the same maximum f-stop but with less depth-of-field control. This suited photographers needing either one of the features above, but not photographers needing both of them in a professional-grade zoom lens.
Basically, very little, very late. They practically didn't produce any primes in the WA and Ultra-WA range except for fish-eye lenses. Coming to zooms, besides a plethora of 18-xx APS-C consumer zooms, generally f/4.5-f/5.6 or similar, we saw the appearance of more "serious" lenses in the 17 to 50-55 mm range with fixed apertures of f/2.8 first, and later of lenses in the 11-12 to 24 mm range with fixed apertures around f/4. While some of them were quite good, these lenses either provided less speed for comparable FOV in FF, or they offered the same maximum f-stop but with less depth-of-field control. This suited photographers needing either one of the features above, but not photographers needing both of them in a professional-grade zoom lens.
What is a professional-grade zoom lens, by the way? Well, besides obviously being whatever lens a professional uses to make money, such a lens in my opinion needs to have:
- constant aperture;
- wide aperture (f/2.8, traditionally, f/4 for longer lenses);
- non-rotating front element;- internal focus and possibly internal zooming as well;
- distance scale;
- fast focussing abilities;
- weather-sealing;
- solid build;
- metal lens mount & body;
- image stabilisation and a good tripod collar & foot (especially for the longer focal lengths).
So why didn't the big manufacturer provide a large offer in the WA and WA-to-normal segment of the market?
The reason for this is, basically, one: Nikon and Canon (and then Sony, when they entered the DSLR market) new that FF cameras would be there someday, and they waited for this to happen so they could:
- move users up to FF (creating upgrade sales = more money);
- save R&D and production costs on professional-grade APS-C lenses.
Third-party manufacturer profited from the lack of efforts of the big guys, and developed some interesting lenses in the WA range for the APS-C market. Very few if any of these, however, has been really professional-grade according to the definition above.
Until now. Sigma finally produced a lens that offers BETTER light gathering capabilities than any FF zoom on the market, WA or not, with the same depth of field control of the equivalent FF zooms. They broke the constant-f/2.8 light barrier for zoom lenses in the process, too, creating the world's fastest constant zoom with an impressive constant aperture of f/1.8. Now APS-C users have a lens with a focal length equivalent to 27-52 mm in FF with an aperture of f1.8, a zoom with the same depth-of-field control of a 27-70 mm f/2.8 zoom but with 1.3 stop more speed at equivalent ISO. Of course, while lens performance data looks pretty impressive on paper I'll have to wait to see whether this lens will perform up to its specifications and up to my expectations before expressing an opinion on its qualities. However, for all the reasons above, this is an impressive achievement already. Pretty impressive, in fact.
So what does this mean for the camera market in general?
According to Sigma at least, this means that APS-C is here to stay. Which leads to a different question: what are the advantages of FF against APS-C?
Traditionally, FF sensors had better light gathering abilities and the possibility of higher resolution; FF camera users had a wider lens choice, especially on WA and Ultra-WA. With the progresses of technology, however, APS-C sensors are closing the gap (except for some particular applications) both in terms of light gathering and resolution; the completeness of pretty much every major manufacturers' lens line-up (or lack thereof) is the most serious challenge left for a professional APS-C user to face.
I definitely hope that this announcement from Sigma will change this situation in two ways. First of all, I hope this lens will be fantastic in terms of image quality as well and not just as far as specifications on paper go, giving APS-C users a new creative tool up to their needing and expectations. But even more than that, I hope this announcement will act as a wake-up alarm ring for Nikon, Canon and Sony, and that they will start taking APS-C more seriously. It would be about time...
So what does this mean for the camera market in general?
According to Sigma at least, this means that APS-C is here to stay. Which leads to a different question: what are the advantages of FF against APS-C?
Traditionally, FF sensors had better light gathering abilities and the possibility of higher resolution; FF camera users had a wider lens choice, especially on WA and Ultra-WA. With the progresses of technology, however, APS-C sensors are closing the gap (except for some particular applications) both in terms of light gathering and resolution; the completeness of pretty much every major manufacturers' lens line-up (or lack thereof) is the most serious challenge left for a professional APS-C user to face.
I definitely hope that this announcement from Sigma will change this situation in two ways. First of all, I hope this lens will be fantastic in terms of image quality as well and not just as far as specifications on paper go, giving APS-C users a new creative tool up to their needing and expectations. But even more than that, I hope this announcement will act as a wake-up alarm ring for Nikon, Canon and Sony, and that they will start taking APS-C more seriously. It would be about time...
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