24-70mm Full-Frame Standard Zooms Head to Head review – Canon, Nikon, Sony
Zooms were treated with a certain amount of derision in the distant past but it wasn’t too long before their advantages became obvious to even the most sceptical commentators. Large numbers of photographers soon started replacing their 28mm, 35mm, 50mm, 85mm, 135mm and 200mm primes with just two zooms, one covering 28-70mm and the other 70-210mm. There was a loss of maximum aperture at some focal lengths but the savings in weight, money and frantic lens-changing that resulted were highly persuasive.
Times change and the old-world 28-70mm zoom is now a 24-70mm, still with an f/2.8 maximum aperture and often boasting a high-speed internal AF motor. Coverage is sufficient for a full-frame sensor and therefore also accommodates APS-C sensors along the way. These are versatile lenses that can be bought once and used for many years on a range of different camera bodies.
Unsurprisingly, many photographers aspire to own one of these highly desirable standard zooms that will cover a wealth of different picture-taking situations. The zooms may not be cheap but the point is that all of them replace at least three prime lenses that would have to have been bought separately in the past.
Anybody who is spending a four-figure sum on a lens is going to expect a high level of performance and these zooms do not disappoint on the image-quality front. That said, none of the 24-70mm f/2.8 zooms is without its own drawback, foremost of which is likely to be an uncomfortably high mass, followed by awkward balance when attached to a modest camera body.
In addition, pictures that are flash-lit using a camera’s pop-up flashgun may reveal a shadow cast by the front of the lens in wide-angle views. This will not concern professional users who prefer hotshoe or hammerhead flashguns but others should be alert to this problem. All users, however, have to be diligent when using filters and other front-of-lens accessories, especially at wideangle settings when vignetting may occur. The costs of skylights and polarisers are also likely to be considerably higher than for more modestly specified lenses. These are fantastic lenses but which is the best – and how, if at all, is their performance likely to change when the zooms are fitted onto a smaller APS-C body?
Canon’s original EF 28-70mm f/2.8L USM was an immediate hit when it was introduced more than ten years ago: such was its fame that it went on to set the standard to which other manufacturers aspired. The 24-70mm version is an update of the 28mm design with an extended close-focusing capability that is marked by a ‘macro’ range on the distance scale.
The lens has Canon’s traditional pro-spec feel: it nestles in the hand comfortably so that the rearmost zoom ring and the forward manual-focusing ring are both within easy reach. There is no movement of the focusing ring in AF mode and the front element is similarly static. Nevertheless, the manual-focusing ring can be employed at any time for adjustment if so desired.
Automatic focusing is brisk and distortion is virtually non-existent. MTF performance is held above 0.3 cycles per pixel from f/5.6 to f/11 at all focal lengths and only falls below the crucial 0.25 figure when the lens is used wide-open or fully stopped-down.
Given that the 0.29x maximum magnification falls a long way short of a 1:1 ratio needed for true macrophotography, Canon has been slightly cheeky in specifically designating the closest focusing distances as a ‘macro’ range (with orange markings on the focusing scale). That said, Canon has used this same tactic on other lenses and many buyers will simply interpret ‘macro’ as indicating an extended close-focusing range.
As with the other lenses on test the EF 24-70mm is by no means cheap, but Canon’s clear intention was to produce a high-spec lens that will appeal to professionals who can off-set equipment purchases against both tax and clients’ invoices. Given this ambition it is worth noting that the 24-70mm has also been weatherproofed to the extent that it is described as being “highly resistant” to dust and water.
Overall, there is little to fault about Canon’s EF 24-70mm in isolation but when set against the brand-new Nikkor design it falls slightly behind in terms of both focusing speed and image quality.
AF-S Nikkor 24-70mm f.2.8G ED & Carl Zeiss 24-70mm f/2.8 ZA Vario-Sonnar T* SSM
Nikon’s brand new 24-70mm zoom is one of those lenses thathas a ridiculously long list of credits in its specifications. The official name indicates only a professional G-series design and the use of extra-low dispersion glass but its subtitle (written on the underside of the lens barrel) adds mention of internal focusing, aspherical profiles, a Silent-Wave Motor and Nano-Crystal coating technology.
To be fair, internal focusing coupled with low-dispersion glasses and aspherical profiles are de rigueur in pro-spec 24-70mm zooms so perhaps it is wise for Nikon to play them down. The Silent-Wave Motor, however, is a raging success: as well as being very quiet it is also amazingly quick and accurate.
The new Nikkor is equally impressive when it comes to image quality. Its MTF curves are above the critical 0.25 cycles per pixel at every aperture and every focal length tested. Peak performance, at 0.3 cycles per pixel and upwards, is obtained between f/5.6 and f/16.
Chromatic aberration, which is undesirable but forgivable in small amounts at the wideangle setting of a zoom such as this, exists only at very low levels indeed and is totally absent at focal lengths above 50mm.
Handling is very good but the considerable length of the lens can result in a slightly unbalanced feel with a more rearward grip, as is required for confident use of the zoom ring. The forward-mounted focusing ring is silky smooth and offers just the right amount of resistance.
The fly in the ointment is the fact that the same considerable length also risks casting a shadow when pictures are taken using a camera’s pop-up flashgun. It is true that this is not a professional’s modus operandi (and this is most certainly a professional’s lens) but in case of emergency it will be frustrating to see an unsightly semi-circle at the bottom of the picture. Perhaps in the future Nikon will design a lens that is every bit as good as this one but also significantly shorter. In the meantime other manufacturers may feel slightly on the back foot when they see what Nikon has already managed to achieve.
Carl Zeiss 24-70mm f/2.8 ZA Vario-Sonnar T* SSM
Sony’s top-rank standard zoom comes courtesy of Carl Zeiss and enjoys the same Vario-Sonnar lineage that made the German manufacturer famous throughout the film-camera world. It is also good-looking thanks to a highly streamlined design that features a constant diameter right along the barrel’s length (excluding the mounting flange itself) and a fairly modest length.
The manual-focusing ring is foremost and has a very good feel; the zoom ring is behind and, on the review sample at least, verges on being slightly too heavy to be truly comfortable. AF speed, provided by an aptly-named Super-Sonic Wave Motor, is good and its accuracy is high. Switching between AF and manual-focusing is carried out using a rotating switch that falls right under the user’s left thumb. Sadly, the rotating action is not as easy on the thumb as a simple slide-switch, which is employed by other manufacturers in this application.
Optically, the CZ 24-70mm zoom displays a well-matched set of MTF curves and it appears that Zeiss has gone more for consistency than for a pronounced sweet-spot in image quality. Wide-open and fully-closed resolutions are slightly lower than elsewhere but from f/4 to f/11 the lens stays solidly in the 0.25-0.30 cycles per pixel range at all focal lengths. There is a small amount of chromatic aberration at the 24mm setting, especially towards the edges of the field but this is unlikely to be obtrusive.
Thanks to internal-focusing there is no movement of the front element, nor of the manual-focusing ring, and with only just over 30mm of extension during zooming (despite a continuous forward movement) this is a very compact lens overall. Even more impressive, given its well-contained proportions, is the fact that the Zeiss lens manages to focus slightly closer than Nikon’s and Canon’s equivalent zooms.
A classy protective pouch is provided with the lens, as is a petal-shape lens hood.
Overall this is a very good-looking lens that produces consistent results right across the range of commonly-used aperture settings, though at a street price of around £1,300 it is also the dearest of the three.
APS-C Performance, Nano Crysal Coating & Conclusion
Some people will say that it would be a waste of money to fit a full-frame lens on an APS-C camera body but the ability to use one lens for two formats is an appealing possibility.
Given that possibility, the next suggestion might be that if a lens performs well over the area of a full-frame sensor then it is bound to do at least as well (and probably better) when used with a smaller sensor. This, however, overlooks the pixel-size issue.
Smaller pixels, as commonly found on smaller-format sensors, have the potential disadvantage of approaching the size of the diffraction disk at small lens apertures. This means that fine detail may be lost sooner when a smaller sensor is used. Similar, but differently originating, effects also appear at wide apertures due to chromatic or other aberrations.
These drawbacks may be partially offset by the fact that an APS-C sensor records its image using only the central area of the lens coverage, and therefore ought to be able to enjoy higher resolution.
As a result, the MTF curve that might be expected when a well-behaved full-frame lens is fitted to an APS-C camera could well include slight drops in performance at the extreme ends of the aperture range but a gain in resolution for other apertures. Significantly, that is exactly what this review has found.
Alongside its full-frame testing, Nikon’s new AF-S 24-70mm f/2.8G ED zoom was also evaluated using a DX-format (APS-C) Nikon D80 body. The MTF curves obtained for the D80 remain tightly entwined and their peak is at a higher resolution but there is a greater curvature to the lines. Only when fully stopped-down is the zoom’s performance (very slightly) worse on the D80 than it is on the D700.
Of course the angle of view also changes and the wide vistas that were previously visible are now considerably restricted but a 70mm picture taken on the D700 would in theory be beaten by a 45mm picture taken on the D80 with the same angle of view. The difference is so slight, however, that it would probably never be visible.
The most important result of this test is not to conclude that a D80 image might theoretically trump one from a more expensive camera but rather to confirm that the very considerable investment that a pro-spec 24-70mm zoom requires will prove justified regardless of the sensor format on which the lens is used.
Every now and again a new technology is added to the list of benefits that lenses enjoy: Nikon’s new Nano-Crystal Coating is one such new arrival. Lenses that have been coated using this technology exhibit considerably less ghosting from off-axis light sources, which is particularly important in wide-angle lenses that have a greater field of off-axis coverage.
The technology was originally developed by Nikon for optical systems that reduce semiconductor designs onto silicon wafers before a way was found to adapt the coating process to mass-manufactured lenses and to toughen it to withstand professional use.
So important does Nikon view its unique new technology that a large N is emblazoned on lenses, including the Nikkor AF-S 24-70mm f/2.8, that have Nano-Crystal Coating. The same technology has also been applied to the AF-S 14-24mm f/2.8 and to the AF-S 300mm f/2.8 prime. Looking at these lenses obliquely in comparison with a conventionally coated lens reveals that Nano-Coated lenses show much less colour on their surface, indicating that the transmitted light is also much less coloured and thereby reducing the obviousness of ghost areas within the image.
For more information go online to: http://imaging.nikon.com/products/imaging/technology/scene/20/index.htm.
All three of these lenses have street prices between £1,000 and £1,300 and all three boast a very high level of build and image quality. They are described as pro-spec lenses and rightly deserve that description.
Sony’s Carl Zeiss lens is the best looking and is also the most compact. Canon’s lens is a solid performer with an excellent pedigree and reputation that only years in the field can secure. Nikon’s lens suffers from its greater barrel length, but it is also the fastest to focus and delivers the best MTF results.
None of these lenses has any serious weaknesses but all could be improved in little ways. Sony’s lens is just a bit too stiff to zoom comfortably; Canon’s lens has the loosest MTF curves; Nikon’s lens casts a shadow when it is used in conjunction with the D700’s pop-up flashgun.
Nikon’s Nano-Crystal Coating technology, which was originally developed for imaging systems used in semi-conductor manufacturing, offers a theoretical advantage that was not investigated as part of this test. That said, the Nikkor produced the most exquisite images of the three lenses examined here. Despite its marginally higher price and slightly awkward size, Nikon’s lens was easily my personal favourite.
That said, there can be no true winners and losers because if you are a Sony user then Sony’s lens is the one that you will buy, and so on. In terms of desirability, however, the Nikkor must come top when the head is making the decisions and the Zeiss will probably win in a beauty contest. The Canon is the one that countless professionals are using but maybe the new Nikkor will change that.