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Zeiss Distagon T* 2.8/25 ZF.2

Introduction:


The Zeiss Distagon 25/2.8 ZF.2 is another excellent Zeiss lens offering to fit Nikon, boasting high build quality consistent throughout the ZF line of lenses. The focusing is precise and butter smooth, allowing for accurate and easy manual focusing.

While most brands make similar lenses with 24mm focal lengths, Zeiss opted to make a 25mm for what I gather was influenced mainly by tradition.


It is important to be aware that the Distagon 25/2.8 has its strengths and weaknesses, and I recommend getting to know the lens before coming to any premature conclusion. I can’t stress enough how easy it is to be blind sighted by lens data such as MTF, resolution, chromatic aberration, and vignetting charts. While this data may help analysing lens performance, it certainly can’t be the given more weight than observations learnt from real world images.


The ZF.2 label designates a built in CPU chip, which is an electronic interface between the lens and the camera. The CPU allows the lens’ aperture to be controlled from the camera, also allowing for automatic exposure modes and transfer of lens data to EXIF.





General impressions and opinions:


The first thing I noticed was its size alongside my Distagon 35/2. The 25/2.8 is shorter and more square-like, which makes it feel somewhat compact. This especially without the hood attached. The lens fits well in hand attached to a D700, and together with the large focus collar, operation is smooth and easy. The lens has a very long focus throw, mainly due to the lens’ ability to focus down to 0.17m, which translates into a magnification ratio of 1:2.3 with full frame cameras. This is very impressive for a wide angle, and some really cool results can be achieved with this lens.


The lens weighs in close to half a kilo, which in my opinion isn’t heavy for an all metal and glass build. Together with the weight and the cold metal feel, the lens gives an impression of longevity and high quality. This impression is again affirmed by the always smooth and easy to turn focus helicoid. Like all the lenses in the ZF line, the cap is terribly flimsy and nothing short of annoying. The 25/2.8 looks and is marked just like all the other ZF lenses; It has a black paint finish with white and red paint markings, and at the front is a chrome-plated brass front bayonet.


Another important aspect for me is that Zeiss made an effort to keep filter thread sizes under control, giving the 25/2.8 a 58mm thread just like the 28/2, 35/2, and 50/1.4 lenses. This means I can use my ND and polariser filters across 4 lenses if need be, which is something that saves me space and money. On that note, the 25mm shows mechanical vignetting with two or more filters attached. When shooting with the Heliopan ND-3 and Polariser attached, quite a lot of cropping was required.





Imaging Characteristics:

(Please NOTE, unless otherwise stated, the opinions expressed are based on experience using a full frame digital camera)


To be honest, after receiving the lens, I didn’t know where or what to shoot. I have read much about the lens online, and both my scepticism and excitement didn’t help. I really wanted to explore the close focusing ability of the lens, but soon noticed it was no easy task.


While the lens can focus extremely close, the sharp and crisp detail is limited to the centre of the image. The lens is not optimised for close range focusing, which makes achieving sharp off-centre detail very difficult even when stopping down. The lens has a very interesting drawing style at extremely close focusing distances, which I can only describe as having a liquid quality to them. While this performance can be exploited artistically, it’s often not very practical.

At close focusing distances, the lens renders quite a smooth and attractive foreground and background blur. Its only in some high contrast scenes that the out of focus (OOF) background detail can be hard edged, and blur disks have a feint bright outline. The background blur depicts the nature of a lens over-corrected for spherical aberrations, which contributes to a harsher background blur at times. For most scenes, the lens renders a very attractive and smooth blur, especially at very close focusing distances.


An annoying aspect of this lens is the noticeable outward running field curvature. While strongest at close focusing distances, it’s still obvious at mid-range to far focusing distances. Stopping down past f/5.6 reduces the field curvature greatly at distances of about 5m and further.  Fortunately it has little influence at very far focus distances, and in general, field curvature shouldn’t be considered a negative aspect. I think it’s more important to be aware of it than assume poor performance at the edges.


With regard to edge performance, the lens is not a weak contender. To me, it lags slightly behind that of the 35/2, but the 25/2.8 is far from bad. Edge performance can easily be determined by focusing with the aid of live view. When shooting landscapes, I would recommend keeping an eye on foreground detail at the edges, which will likely be the least sharp areas of an image when shooting near or at infinity. I suggest focusing slightly before infinity or using live view to determine the sharp infinity mark at the edges, and then stopping down to control depth of field of the image centre. Understanding the field curvature of this lens is very important, because it may not be ideal for certain subjects, especially for medium to close distance planar subjects, as the curvature can have a strong negative effect on corner sharpness.


Overall, the image quality of this lens is very good, but not extraordinary. Both the contrast and micro-contrast are high straight from f/2.8, and the lens is capable of rendering high acutance images with much detail and “pop”. The high micro-contrast is instrumental at creating good subject isolation, which is something this lens and many other Zeiss lenses are known for. Colour rendition is also consistent with that of the ZF line, and I’ve never felt the need to find fault with the way the ZF lenses render. The results have always been pleasing.


The lens doesn’t have obvious signs of axial colour aberration, but the lens does have moderate to high amounts of lateral chromatic aberration. From the shots I’ve taken, I can’t say that the lateral CA is excessively high, which conflicts with what others have written about this lens. Lateral CA is easy to correct in most cases, but the lateral colour aberration evident in some high contrast blur disks is not easy to correct. Other than that, I haven’t come across any obvious signs of coma flare and astigmatism. Night shots with point light sources will show just a little coma, and these slightly elongated points at the frame edges are largely eliminated by stopping down to f/5.6.


Much like the 35/2, the 25/2.8 is also very resistance to flare and ghosting, likely thanks to the fantastic T* coatings.

It’s not completely impervious to flare and ghosting, and a few light spots or streaks can be seen when shooting into the sun. Overall it’s an excellent performer, capable of maintaining high contrast when shooting into strong light. The supplied lens hood is, of course, invaluable, and I recommend it at all times. When not used to prevent stray light entering the lens, it will offer protection from damaging the front element. While the T* coatings are quite hardy, I still recommend the extra protection of a hood so that the need of a UV or clear-glass filter is kept to a minimum. I can only recommend a UV or clear glass filter in adverse shooting conditions such as those at the ocean.


The lens shows some moderate barrel distortion, which is hardly noticeable in most cases. According to graphs, the barrel distortion has a slight moustache property with its lip at the far edges, but I haven’t seen obvious signs of it. If correction is needed, I think it’s sufficient to apply one for regular barrel distortion. It’s only for architectural purposes that the lens’ distortion signature play an important role, but for most other applications I would not lay too much weight on this.


The biggest gripe I have with this lens is very strong vignetting. The vignetting or light fall-off is so strong, that light transmittance in a aperture series is greatly unequal. For an exposure to suit shooting at f/2.8, a corresponding exposure for

f/5.6 will cause a fairly high over-exposure. I have a few aperture series on page 3 where this problem can be clearly observed. Personally, this could be considered a deal breaker, especially if one relies on quick auto exposure to “get the shot”.

For landscape shooting this isn’t a problem, but I imagine for fast actioned street photography this must become incredibly annoying.


I haven’t had much opportunity to try this lens on my D2x infrared camera. From my short experience with the combination, it seems this lens fares much better than the 35/2. I haven’t seen any signs of a hotspot, and the closest resemblance would be subtle ghosting when shooting in high contrast scenes. This is about as far as I can take the infrared performance evaluation.

On page 3 I have included one sample image taken with the D2x-IR camera.





Conclusion:


The Distagon 25/2.8 is a very nice lens, and it certainly has appeal. To get the best from the lens, it should first be understood, especially with regard to its field curvature and close focus performance. Not understanding these can result in a poor user experience. The overall imagery of the lens is very pleasing, and like the rest of the ZF range, the 25/2.8 boasts high contrast and micro-contrast from its widest aperture. Along with the drawing style, smooth OOF rendering and unique close focusing performance, this is a very attractive lens, capable of some amazing and high quality results. Lateral CA isn’t troublesome and sharpness is good all around, especially if the field curvature contributes to sharper edges. However, field curvature is not always a welcome feature, and most annoying is the incredible vignetting. Also, being a f/2.8 lens, the viewfinder will appear a little darker, making unaided focusing slightly harder than the f/2 ZF lenses.


To conclude, this very capable lens is set back by its field curvature and strong vignetting. These are two strong arguments against this lens, which need careful evaluation. If you are considering purchasing, my advice is to rent or borrow this lens, it may make all the difference.