Zeiss Loxia 25mm f/2.4
Andy Westlake tests this compact manualfocus prime
Whenever Zeiss brings out a new lens, chances are it’ll be something special. With the Loxia 25mm f/2.4, however, you might be forgiven for wondering what the firm is thinking. It’s not that this small manualfocus wideangle prime looks undesirable – quite the opposite. However, its £1,190 price tag is significantly higher than Zeiss’s own autofocus Batis 25mm f/2, which costs around £1,000 and gives superb results. So why pay extra for a slower lens you have to focus yourself?
The answer, of course, is that many serious photographers value the shooting experience this brings. The fully manual operation is also advantageous for video work, where it’s essential for any adjustments to be smooth and silent. Even so, any f/2.4 manual-focus prime is going to have to be seriously good to justify this kind of price tag.
Features
In Zeiss’s idiosyncratically named line- up, its Loxia lenses all come with a common set of characteristics. They’re fully manual primes designed for use on Sony’s full-frame mirrorless cameras, and combine top-notch optics with compact size and high- quality weather-sealed construction. The 25mm f/2.4 is the fifth lens in the series, and all share the same 62mm barrel diameter and 52mm filter thread, along with matching cosmetic designs.
Of a Distagon-type retrofocal design, the Loxia 25mm f/2.4 has 10 elements arranged in eight groups. Two anomalous partial dispersion glass elements are used to combat chromatic aberration, while an aspherical element suppresses curvilinear distortion. Zeiss’s T* coating minimises flare and ghosting, and a petal-type metal hood is supplied.
Aperture operation is completely manual, using a ring on the lens that stops the aperture down directly as it’s turned. This means you always get a completely accurate depth- offield preview in the viewfinder. However, only aperture-priority or fully manual-
exposure modes are available, and you can’t change the aperture using the electronic dials on the camera body.
The diaphragm itself is formed of 10 straight- edged blades that form a distinctly decagonal shape when it’s stopped down. This may seem odd in an age when almost every new lens boasts a circular aperture for attractive bokeh, but it’s of little consequence. This kind of relatively slow wideangle won’t give much in the way of background blur anyway.
While the lens may look just like an oldfashioned manual-focus prime, in one crucial respect it’s quite different. A set of electronic contacts in the mount transfers key information back to the camera, so the selected aperture is always displayed in the viewfinder and recorded in EXIF data. The lens also recognises when its focus ring is turned, and can trigger magnified view in the camera’s viewfinder for as accurate focusing as possible. Last but not least, the focal length is passed to the camera body for inclusion in the EXIF and to ensure the in-body image-stabilisation system works correctly.
Build and handling
We’ve come to expect superb build quality from Zeiss, but if anything the Loxia feels a step above the firm’s Batis and Milvus designs. The entire outer barrel is made from metal, including the manual-focus and aperture rings, which have finely ridged, tactile grips, along with engraved distance, depth- of-field and aperture markings. To round things off, a blue silicone seal around the mount protects the interface with the camera from dust and water ingress. Overall, this lens feels like a very special, lovingly crafted tool.
The manual-focus ring covers the front twothirds of the barrel, including the area in front of the ridged grip itself. It rotates very smoothly with just the right amount of resistance. The grip falls naturally into your fingers, so you’ll never be fumbling to locate it in a hurry.
Pull your fingers back towards the camera body and you’ll easily locate the slimmer aperture ring, which clicks at one-third stop detents. Again, the stiffness of the clicks is perfectly judged, so you’re unlikely to change settings inadvertently. If you prefer a smoothly rotating aperture ring, then rotating a small screw that’s inset into the lens mount through 180° will de- click this control, and a tool is provided in the box for just this purpose.
If I have one small criticism of the handling, it’s that there’s little non- rotating real estate on the barrel to grasp when attaching or removing the lens. This makes changing lenses a bit slower and more awkward than it should be.
Focusing
The focus ring rotates 90° from the infinity position to the minimum object distance of 25cm, which gave sufficient control for really precise focusing. The entire optical unit shifts backwards and forwards by a few millimetres in the process – an approach that Zeiss says should give maximum sharpness but which is generally impractical on autofocus lenses, as they demand small, light internal focus groups to maximise AF speed. I set the camera to activate 10x magnified live view when I turned the focus ring, and found this made it easy to achieve perfect focus, shot after shot. With manual focus implemented this well, I barely missed having autofocus at all.
Performance
At the start of this review, I stated that any manual-focus lens offering an f/2.4 aperture for nearly £1,200 had better be seriously good, and luckily that’s just what the Loxia is. It’s more accurately described as sensational.
Sharpness is phenomenal. Even when shooting at f/2.4, the level of detail recorded in the centre of the frame matches many other lenses at their best aperture. It’s only in the extreme corners that there’s any obvious degree of smearing. Close down to f/8 and the lens delivers the kind of corner-to- corner excellence that’s the preserve of only the very finest optics, easily satisfying the demands of the 42.4MP sensor in the Sony Alpha 7R II and III.
Other lens flaws are notable mainly by their absence. If you pixel-peep, you’ll find some colour fringing in out- of-focus areas at f/2.4 due to longitudinal chromatic aberration, and a little in the corners from the lateral variety. But it’s trivial to fix in post-processing. Meanwhile, distortion is nearly perfectly corrected, with just the slightest hint of barrel-type curvature in lines placed along the long edges of the frame. Activate in- camera distortion compensation and it disappears completely.
Point the lens directly into the sun and it’s completely unfazed, with barely any hint of flare. At small apertures you’ll see 10-ray sunstars from the 10-bladed aperture diaphragm.
This just leaves vignetting, which is noticeable wide open, but becomes almost imperceptible on stopping down to f/5.6. There’s a school of thought that any vignetting counts as a flaw for which a lens should be criticised, but I don’t subscribe to this view at all. I prefer to consider vignetting as an optical characteristic, which in the right circumstances can enhance your shots. On the Loxia, the edge- darkening effect is quite gradual and visually pleasing, and on more than one occasion I deliberately shot at f/2.4 to exploit its aesthetic quality, safe in the knowledge that I wasn’t compromising detail along the way.