Zeiss Loxia 21mm f/2.8 Lens Review

What is It?
The Zeiss Loxia 21mm is a manual focus wide angle lens that can be used with any of the Sony mirrorless cameras (E or FE). It’s the lens I tend to point to when asked if there are any advantages to the shorter mount-to-sensor distance of mirrorless cameras over DSLRs.

Generally the place where a lens designer can be more flexible and creative with lens designs for a mirrorless camera is in the wide angle to normal range. At telephoto focal lengths, there’s little advantage to be gained in terms of length and diameter of the final lens, regardless of mount distance or the size of the imaging circle the sensor requires. As I like to put it, a 300mm f/2.8 lens is going to have its front about 300mm from the sensor and a diameter of 300 divided by 2.8. There are some exceptions to this, but it requires non-traditional optical design, such as Canon’s Diffraction Optics or Nikon’s Phase Fresnel approach.

But at the wide angle end, there’s a lot that can be gained by having a short mount distance: you really can make a smaller, lighter lens without having to invent a whole new optical approach. Indeed, many early film SLR wide angle lenses required that you lock the mirror of the camera up so that the rear elements could be close to the focal plane (film in those days, imaging sensors today).

Zeiss, very obviously, has come up with a design that takes advantage of the close mount/sensor relationship. Indeed, the 21mm f/2.8 is so small, I originally started using it on my A6300 (crop sensor) camera because it is very well balanced on the front of that camera. Not too big, not incredibly small. Sort of a Goldilocks sort of thing: just enough lens to put my hand under for support while shooting, not too much lens to poke way out in front of the camera.

I’m getting ahead of myself, though. That’s a handling discussion. Still, this is a lens that immediately strikes you as small and appropriate for mirrorless cameras. Ironically, my Nikkor 20mm f/2.8 is shorter, and also diminutive, but it’s also a very old and simple optical design.

So what’s the actual size and weight? 2.8” (72mm) in length, less in diameter, and 13.9 ounces (394g).

Internally, the design features 11 elements in 9 groups, with one aspherical and four anomalous dispersion pieces of glass. Not a complex design, but one that is modern.

A 10-blade aperture diaphragm is controlled by a physical aperture ring near the lens mount. There are click stops from f/2.8 to f/22 at every third of a stop, though the lens can be changed to continuously variable—declicked in Zeiss parlance—with a small tool Zeiss provides. You’d want to make that alteration if you’re shooting video using this lens, as the click stops would disrupt you producing an even aperture transition if your exposure changed while shooting video.

Just in front of the marked aperture ring is a set of depth of field markings for f/4, f/8, f/16, and f/22. And finally, just in front of the depth of field markings is the focus ring markings:

  • 0.9, 1, 1.2, 1.5, 2, 3, 5 plus infinity for feet
  • 0.25, 0.3, 0.4, 0.5, 1, 2 plus infinity for meters

Looking down at the top of the lens tells you aperture, focus point, and depth of field in one convenient glance. Indeed, this design or markings will almost certainly provoke a severe “retro” nostalgia in almost anyone who shot with the better lenses in the film era. With so much electronic and only reported in viewfinder/LCD if reported at all these days, you’ll find that the simple, traditional approach Zeiss has used on this lens is immediately welcome.

That’s not to say the lens isn’t reporting aperture and focus data electronically to the camera. It does. Indeed, one of the best design features of the lens is the combination of traditional and modern: this is a manual focus lens, but if you turn the focus ring on the lens, the default behavior of the Sony bodies will be to immediately put you into magnification mode in the EVF/LCD so that you can better evaluate the focus. Bravo. This is the reason why you buy a modern lens over trying to adapt some old lens you have: it works seamlessly and provides a clear working advantage.

Up front, we have a 52mm filter thread, and Zeiss supplies a petal shaped lens hood that bayonets onto the front of the lens. Lens length and front element position do not change during focus.

Zeiss's page for the lens is here. The lens sells for US$ 1500 and is made in Japan.

This review is based on one sample borrowed from B&H.

How’s it Handle?
In a word: smooth.

The focus ring turns from minimum to maximum distance is just over a quarter turn, and it does so fairly quietly and very smoothly. At this lens’ price and with Zeiss’s name on it, that’s exactly what you’d expect, but it’s always nice when things turn out as you’d expect.

But smooth has a derogatory element to it, too. If I have any complaint at all about the lens, it’s that the two control rings have very subtle texture to them, and are therefore a little more difficult to find by feel than you might expect. That’s particularly true of the aperture ring.

And yes, I know this next one will be probably the nitpick to end all nitpicks, but…

The lens mount alignment mark on the Sony cameras and lenses is an easy to see white. Even in low light. The lens alignment mark on the 21mm Loxia is a darkish "Zeiss blue", and somewhat difficult to see in the dark. Indeed, I was in a dim environment when I first tried to put the lens on a camera. I was looking for a white marker. Didn’t find it. Took me a moment to notice the dark blue one.

So yes, a nitpick, but please make the alignment markers match the camera, Zeiss. If Zeiss were to follow the marketing logic of making things blue—an indentity ring right at the back of the lens is also blue—we’d have blue aperture labels, depth of field markings, and focus markings. Yeah, Zeiss didn’t do that because we’d never see them in dim light. So why is the lens alignment marker blue? ;~)

Lest you get the wrong opinion, I don’t really have any major objections to the way this lens handles. Just wish that the rings had a bit more texture to them so as to be easier to find, and that the lens alignment marker was more visible. Not flaws I’d lower my evaluation of the lens on, at all.

How’s it Perform?

Let’s get one thing clear up front: the lens shows some field curvature. Indeed, using the Loxia I was reminded of the same things I have to be aware of when using my Nikkor 14-24mm f/2.8: at distance there will be clear field curvature. You need to back focus a bit with all-distant subjects to keep corners and center near identical. That’s not the way I usually shoot a wide angle lens, as I’m almost always putting near depth cues into the frame, so I definitely saw some modest field curvature effects in the far objects.

Wide open the Loxia is sharp. Excellent in the center and very good in the corners. Stop down a bit, and I’d say that edge-to-edge gets into the exceptional realm, something I rarely ever write about a lens. And that’s assessing the lens on a 42mp A7rII, which really should tell you something. On the crop-sensor A6300 edge to edge is impressively excellent wide open. I doubt anyone’s going to be complaining about how well this lens resolves detail.

Lateral chromatic aberration is present, but highly correctable. I didn’t find much longitudinal chromatic aberration, either, which is a little surprising for a prime at f/2.8. Indeed, I’d say the Loxia is better behaved at chromatic aberration than most Zeiss lenses I’ve used, which tend to have clearly visible CA.

Linearity is a mixed bag. While there’s not a lot of linear distortion, it’s barrel in the middle of the frame (and on APS bodies) with pincushion in the full frame edges. Clearly mustache-type distortion, and a bit difficult to correct exactly. The in-camera tables do a good job of correcting this, but not perfectly.

Vignetting isn’t nearly as bad as I was expecting. Yes, with JPEGs on an A7 body it’s visible and still needs correcting (maybe 1.3 stops worth), but stop down even to f/4 and it becomes mostly ignorable. For such a wide angle lens, the vignetting performance is good, but that doesn’t mean that it doesn’t vignette ;~). In raw files, the vignetting exceeds two stops, and definitely needs correcting.

Flare is clearly evident on light sources in the frame, though very modest in nature. None of the complex, multi-color rainbow stuff I see with some other wide angle lenses, but more of a simple repeating flare bubble.

Bokeh isn’t something you usually write about with wide angle lenses. But if you get close enough to your subject wide open, it might start to come into play. I’d call the bokeh slightly busy, but very well behaved with no really visible edge effects.

Overall, this lens is a winner. The sharpness and contrast are about as good as you’ll find in a wide angle prime, and the other attributes don’t really detract from that.

Final Words
In a word: lovely. High quality build, really smooth focus ring (in both respects), nice and highly visible informational markings, good integration with the camera’s smarts (automatic magnification on focus), and some really great optical characteristics. All in a small, easy to transport package. Why would I not like this lens?

Well, the kicker for many would be price. It’s not inexpensive. Indeed, it is expensive. There, I said it (actually, I wrote it). And it is manual focus with a slightly slippery focus ring. So you really have to want a lens like this to opt for it.

The good news is that if you want a manual focus 21mm lens that covers the full frame of the A7 cameras and delivers performance that looks good even at 42mp, then you’ve found your lens. This is a great companion to the Sony A7rII for when you want to go wide and tightly control focus yourself. I suspect that street and landscape photographers will be the ones that most respond to this lens.

I certainly can recommend it, though at the price I really want more texture on the focus ring than the Loxia 21mm gives me. As usual with Zeiss, there’s a punch to the images produced with this lens that you often don’t see using zooms and lower-priced optics. And that punch is what a lot of you are looking for: better edge acuity coupled with a bit more overall scene contrast makes great images look greater.


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