Carl Zeiss Distagon T* 2.8/21 ZF.2 lens review

Introduction Carl Zeiss "ZF" line of lenses was introduced in January 2006. The lenses feature manual focusing and are designed to be used on Nikon F mount cameras. The original ZF lenses come with the features that users of the classic Nikon SLR cameras expect to have: Nikon F bayonet, automatic close–down aperture, the same rotation direction of focus and aperture ring, second aperture scale to enable optical readout of the aperture in the viewfinder and AI coupling fork. The lenses, however, do not have any electronics and thus there is no electronic communication with the camera. In practice this means that one has to input lens data (focal length and maximum aperture) in the camera and set aperture on the lens.

In November 2009 the original ZF line was upgraded to ZF.2. The updated lenses no longer have the pre–AI coupling fork, due to which light metering cannot be used on older Nikon cameras (F, F2, Nikkormat, etc.). Very importantly, however, they boast electronic interface thus allowing full support of automatic exposure modes and inclusion of lens–related data in EXIF. At the same time, ZF.2 lenses have a mechanical lock on the aperture ring to lock the aperture ring at the smallest aperture setting. There is no difference between ZF and ZF.2 lenses in terms of optics.

The lens was tested on a 12MP Nikon D700 camera. FX format cameras of higher resolution will put a further emphasis on some of the performance deficiencies reported in the review. At the same time, vignetting, distortion and corner sharpness will be less problematic when the lens is used on DX format cameras.

Build quality, focusing and handling

The lens is made of metal and built like the proverbial tank; every aspect of its construction exudes quality. Operation of the focus ring is smooth and buttery; operation of the aperture ring, on the other hand, is fluid yet firm. Front element does not rotate as you focus the lens, which makes using polarizing and graduated ND filters easy.

The lens is fairly heavy (600g) and quite large. When mounted on a camera, the lens–and–camera combo feels quite bulky, especially due to the uncommonly large front of the lens. The lens takes 82mm filters, which is an unusual size and might require buying additional filters specifically for this lens.

Sharpness

It is understandable why most photographers usually put more emphasis on sharpness than on other optical performance factors—while such aberrations as distortion, vignetting, etc. will be seen only in some images and, at least partially, can be dealt with in post processing, soft corners will be visible in most, if not all, photographs and cannot be remedied after the fact. Thus, let us first see how the lenses perform in the department of sharpness. The images below are crops from the original test shots shown at 100% magnification; no sharpening was applied to any of them.

Centre

Corner

f/2.8

f/8

The test shots and my overall experience with the lens indicate that it is impeccably sharp, centre to corner, starting right from f/2.8—to the extent that it can be used as a benchmark for evaluating other lenses. If you resort to hardcore pixel peeping, there is a very slight loss of sharpens in the farthest corners at f/2.8; this, however, is unlikely to be noticeable in reasonably sized prints.

Vignetting

The test shots below were taken at the same EV (exposure value). The lens apparently has a small image circle and shows very strong vignetting at f/2.8—it actually is more akin to overall underexposure than light fall–off. At this aperture the aberration will be seen in most real life photographs. It is very difficult to completely remove in post processing but can be reduced to a level where it is less objectionable.

	f/2.8		f/4
	f/5.6		f/8

Vignetting is still very noticeable at f/4 and is reasonably controlled only by f/5.6 (but still will be visible in some photographs); for all intent and purposes it is mostly gone by f/8.

Distortion

As can be seen in the photograph below, the lens exhibits predominantly pincushion distortion that has a slightly complex (wavy) signature. Its degree, however, is very, very low and you will not see it in most photographs. In fact, given how wide the lens is, one has to go out of his way to find pictures where the aberration is noticeable.

Chromatic aberration

Chromatic aberration is exemplarily controlled. Tiny amount of colour fringing can be seen around high contrast edges; rather than being a thorn in the eye, however, it is something that you have to purposefully look for. Colour fringing is manifested as lateral chromatic aberration that can be easily removed in post processing; I could not detect any immediately visible longitudinal chromatic aberration.

Flare

The lens is extremely flare resistant, which is nothing short of astounding given the lens' large front element and how complex the lens is optically (16 elements in 13 groups). I purposefully tried to induce image degradation from flare by shooting into bright sun on various occasions, but failed. Only once did I see a small, subdued aperture ghost in an image shot at f/22. The photograph in the Distortion part of the review illustrates this point—the reflection on the building was very, very bright.

Bokeh

The Carl Zeiss Distagon T* 2.8/21 ZF.2 is an ultra wide angle lens and bokeh will not be of a major concern in most situations. Nevertheless, if you are interested, bokeh is fairly neutral at f/2.8 and smaller apertures.

Final thoughts

The lens is a spectacular optic and easily one of the best performers across various brands at this focal length. Its only real drawback is very strong vignetting at f/2.8, but then again many ultra wide angle lenses have this quality. If you need a lens of this focal length for nature or landscape photography and do not mind the bulk (and the price tag), I recommend the Carl Zeiss Distagon T* 2.8/21 ZF.2 without reservations.