Sony FE 24-70mm f/4 ZA OSS Zeiss Vario-Tessar T* SEL2470Z

SLRgear Review
March 28, 2014
by William Brawley

The Sony FE 24-70mm ƒ/4 ZA OSS Carl Zeiss Vario-Tessar T* was one of the two new zoom lenses announced alongside the full-frame Sony A7R and A7 mirrorless cameras. This Carl Zeiss-branded lens features a very versatile 24-70mm focal length range making it suitable for landscapes, portraits and pretty much everything in between.

The lens includes a variety of high-end features like Sony's Optical SteadyShot image stabilization technology, Carl Zeiss' T* coatings for reduced flare and boosted contrast, and a rugged build quality that's resistant to dust and moisture.

This compact full-frame zoom lens ships with a bayonet-style lens hood, front and rear caps and a soft pouch. The Sony FE 24-70mm ƒ/4 ZA OSS Carl Zeiss Vario-Tessar T* is currently available for purchase for a retail price around $1,198 - (Adorama, Amazon, B&H).

Sharpness
Despite carrying the Zeiss branding, which is typically indicative of high-end results, we felt that the Sony FE 24-70 Zeiss lens fell a little short of our expectations. At 24mm, the lens displays good sharpness right in the center of the frame, even wide open, but outwards and especially in the deep corners it's noticeably soft. Surprisingly, even stopping down doesn't improve the corner softness at 24mm, and by ƒ/16-ƒ/22, diffraction comes into play and reduces sharpness all around even more.

Zooming out to 35mm and 50mm improves sharpness significantly, especially in the corners, and throughout the aperture range (until diffraction hits at ƒ/22). However, as we saw at 24mm, 70mm on the Sony FE 24-70 displays a decently sharp center, but with considerably softer corners that aren't much improved by stopping down. Surprisingly, corners at 70mm appear even softer than they do at 24mm.

All in all, we were a little surprised to see a Zeiss-branded lens be as soft in the corners as the Sony FE 24-70mm f/4 was. It's perhaps important to note, though, that we base our testing on RAW file output, so it's very likely that Sony cameras will apply significant in-camera correction to the JPEG images, resulting in much more uniform sharpness.

Chromatic Aberration
The Sony FE 24-70 Zeiss lens does quite well in controlling chromatic aberration. At all focal lengths, and all apertures, the lens displays very low CA on average. The lowest amount of CA is at 50mm, which hovers just above zero at ƒ/4. We saw a little up-tick in average CA at 70mm ƒ/4, but it was still very minor, and something that would easily be alleviated by in-camera JPEG processing or quick adjustment in your favorite photo editing program.

Shading (''Vignetting'')
If you're a fan of vignetting, you're in luck, as the Sony FE 24-70 shows a lot of it, particularly at 24mm. Wide open at 24mm, the lens shows over 1.5 stops of light loss, and even by ƒ/5.6, it's still over 1 stop. Stopping all the way down to ƒ/16-ƒ/22, vignetting still shows over 0.5EV of light falloff.

The longer focal lengths fair better, but the three other focal lengths we tested (35mm, 50mm and 70m) all display significant vignetting from ƒ/4 until around ƒ/8. Stopping down past ƒ/8 still shows moderate vignetting at these focal lengths. Interestingly, 70mm shows the next highest amount of vignetting when shot wide-open at just under 1 EV of light loss.

Shading is quite easy to correct for, so here again, JPEG results on Sony cameras could be considerably better than what we're seeing in the RAW files.

Distortion
The geometric distortion characteristic of this lens is rather complex. On average (meaning, affecting most of the frame), there's barrel distortion to a varying degree at all focal lengths, even the more normal and telephoto focal lengths of 50mm-70mm. At 24mm, barrel distortion is the strongest, between 0.5-1%, while 35mm shows the least, at around 0.2%. However, when you look at the maximum distortion values, which generally show what's going on around the edges of the frame and in the corners, we see over 1% barrel distortion at 24mm, yet close to -1% pincushion distortion at 35mm and even more pincushion distortion at 50mm and 70mm (almost -1.5%).

At the risk of sounding repetitious, distortion is also something that's subject to in-camera correction, and in this case would be better done there than in Photoshop or Lightroom, given its complex character, with both pincushion and barrel distortion being present within the frame at the same time.

NOTE: We normally ignore in-camera JPEG results, because the in-camera processing introduces too many variables to permit good comparisons between lenses on different platforms. Given the extent of corner softness, shading, and distortion we've found in the Sony FE 24-70mm f/4 lens, though, we're going to take a look at some camera JPEG images captured along with the RAWs used for this analysis, to see to what extent in-camera correction addresses some of these issues. Stay tuned for an update on that within the next week or so.

Focusing
The Sony FE 24-70 Zeiss lens autofocuses very quickly, taking under one second to focus through the whole range. Nice and fast. It's also extremely quiet. It should be noted, however, that by default, the Sony A7R and A7 cameras have a "Pre-AF" setting enabled, which makes the camera continually focus, which can help speed up focusing as the lens may already be near the appropriate focus distance for whatever you're shooting. This setting can be disabled, though, as we found it can be distracting as well as impact battery life.

Manual focusing is also available on this lens, though like other Sony FE lenses, it uses an electrical focus-by-wire system. The focus ring on the lens will therefore rotate smoothly, but indefinitely with no stops at minimum and infinity focus distances. Also a consequence of the focus-by-wire design, there are no focus distance markings or window on this lens.

Macro
The Sony FE 24-70 Zeiss has a close focusing distance of 1.32ft (40cm) with a maximum magnification of 0.2x (1:5 ratio), which doesn't make it a great lens for macro photography.

Build Quality and Handling
Like the other Sony FE lenses released so far, the Sony FE 24-70 Zeiss has excellent build quality. It has a solid feel and slight heft, while still being compact, lightweight and relatively well-balanced on the A7/R cameras (there's a bit of front-heaviness to it, but it's not awkward to use by any means).

The zoom and focus rings rotate very smoothly with just the right about of dampening -- not too stiff but not loose either to cause concern for lens creep. The lens extends slightly when zooming making it about 1.25 inches longer at 70mm. The front element does not rotate during focusing or zooming making the lens suitable for filters such as circular polarizers (with 67mm filter threads).

Keeping with a similar design aesthetic to other Sony FE lenses, the Sony FE 24-70mm Zeiss lens features a metal barrel with a very nice, smooth, matte black finish, and fine-grained ribbed textures on the focus and zoom rings. The all-metal construction is designed to protect against dust and spray, but it is most likely not fully weather-sealed (i.e. there's no rubberized gasket around the mount). Inside the barrel sit 12 elements in 10 groups, including 5 aspheric and 1 extra-low dispersion elements. The 7-bladed, rounded aperture diaphragm makes out of focus areas pleasing and smooth.

When it comes to buttons, rings or other exterior features, like the FE prime lenses, the FE 24-70 is fairly sparse with its zoom and focus, and not much else. Since the lens is a focus-by-wire system, there's no focus distance window built-in to the lens, nor is there a manual AF/MF toggle switch or an On/Off switch for the Optical SteadyShot system either -- those are controlled via the camera.

Alternatives
Sony does offer an alternative to the pricey $1000+ Zeiss-branded 24-70mm ƒ/4 lens -- the Sony FE 28-70mm ƒ/3.5-5.6 OSS. This zoom lens not only provides a similar range of focal lengths -- thought not as wide -- but also built-in image stabilization. You do, however, loose the constant ƒ/4 aperture as well as the all-metal construction (that lens is mostly plastic, though it does have a metal lens mount like its Zeiss sibling). The big plus is that it's significantly more affordable with a retail price just shy of $500.

However, seeing as the Sony FE mount is the new kid in town, there aren't many third-party alternativse yet. However, with Sony's own LA-EA3 A-mount to E-mount adapter (no AF) or LA-EA4 adapter (adds Sony's Translucent Mirror technology and autofocus), you could use Sony A-mount lenses, including the large and heavy Sony 24-70mm ƒ/2.8 ZA Carl Zeiss Vario Sonnar T*, which features a much brighter constant ƒ/2.8 aperture, but no image stabilization and a whopping $1,800 price tag. There's also the Sony 28-75mm ƒ/2.8, which sacrifices a bit of the wide end and adds a slight increase in focal length at the tele, as well as having a constant ƒ/2.8 aperture. However, again, you don't get image stabilization, but you do have a slightly more affordable price at around $900.

Now, the smaller flange distance of the Sony A7R and A7 makes using adapters with a wide variety of third party lenses quite simple, as the A7R/A7 use a standard Sony E-mount. There are other adapters out there allowing users to mount Canon EF lenses and Nikon F-mount glass to E-mount cameras, and the resulting combinations would be too much to list here. It's certainly worth knowing that the Sony A7R and A7 provide a very flexible full-frame camera platform for fans of lenses from a variety of manufacturers.

Conclusion
After seeing superb results from the two Sony/Zeiss FE primes, the 55mm ƒ/1.8 and 35mm ƒ/2.8, we had high hopes that the Zeiss-branded 24-70 ƒ/4 lens would be another excellent piece of glass. In terms of build quality, the Sony FE 24-70 Zeiss is indeed excellent, with an all-metal construction and that characteristic Sony and Zeiss matte black design. When it comes to RAW-file image quality, however, we found ourselves a little disappointed. With soft corners at essentially all focal lengths (and even stopped down), plus strong vignetting and distortion, the Sony FE 24-70mm ƒ/4 ZA OSS Carl Zeiss Vario-Tessar T* didn't meet our expectations. It's possible that default corrections applied in-camera to the JPEG files may counteract some of these issues; we'll be investigating that possibility a bit further, and will report back here with the results.

For fans of landscape photography who demand sharp images corner-to-corner and low vignetting, and who primarily work from RAW images, this may not be the lens for you. And even for RAW shooters doing general-purpose photography, for which a 24-70mm lens is very useful, the Sony FE 24-70 Zeiss lens comes with a hefty price tag that doesn't deliver the kind of performance we'd expect. For JPEG shooters, stay tuned for an update here, after we've had a chance to do some analysis on some in-camera JPEG images.

Thankfully, the Sony A7/R cameras are very flexible when it comes to adapters, so fans of wide-angle and general-purpose focal lengths aren't left out in the cold as lenses from Sony's A-mount lineup or even other manufactures can easily be used. And there are always the excellent Sony FE primes as another, albeit slightly less versatile, option for the Sony A7/R photographer.

Product Photos

Sample Photos

Note: We only had this lens in-house for a brief time, and as such, we were only able to fully test it on the Sony A7R. However, we have included sub-frame sample images from the Sony NEX-7.

Check out some sample photos shot by our senior lens technician Rob Murray. You can view more sample photos, plus download the full-resolution files, over at our Flickr page.

The VFA target should give you a good idea of sharpness in the center and corners, as well as some idea of the extent of barrel or pincushion distortion and chromatic aberration, while the Still Life subject may help in judging contrast and color. We shoot both images using the default JPEG settings and manual white balance of our test bodies, so the images should be quite consistent from lens to lens.

Still Life shot

VFA target

As appropriate, we shoot these with both full-frame and sub-frame bodies, at a range of focal lengths, and at both maximum aperture and ƒ/8. For the ''VFA'' target (the viewfinder accuracy target from Imaging Resource), we also provide sample crops from the center and upper-left corner of each shot, so you can quickly get a sense of relative sharpness, without having to download and inspect the full-res images. To avoid space limitations with the layout of our review pages, indexes to the test shots launch in separate windows.