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Field Tests

The original Contax Carl Zeiss Distagon T* 35mm f/1.4 lens was first introduced in mid 70s, although the original design see in Contax branded version was first introduced for the Rollei 35 mount in mid 60s. While Distagon design spans both SLR as well as rangefinder lenses (for example, the 18mm Distagon is available for both rangefinder as well as SLR systems), the 35mm variant of the design, as far as I am aware, was only available for SLR cameras, with an equivalent rangefinder design being the Biogon. However, unlike the previous versions, Contax Distagon 35mm design was the first to use a floating element. The major benefit of a floating design obviously is the improved performance at close distances, although a floating design does not necessarily automatically guarantee a better performance. In the case of the Distagon, the floating element, which is typically placed as the  rearmost element in the last lens group, is the probable cause for numerous reports of incompatibility with some of Canon's full frame cameras, particularly Canon 5D and Canon 5D MkII. Now, I have had the opportunity to test both AE as well as an MM versions of the lens, and did not encounter any problems with the camera's mirror clearance. Not to say that the reports are wrong, since in many cases, the variance in the mirror  box assembly can contribute to the problem.

A more appropriate question however, is whether the floating design of Contax Carl Zeiss Distagon T* 35mm f/1.4 actually delivers better image quality at close distances. Resolution-wise, at least, this did not seem to be the case, as the lens did not show noticeable improvement at close distances over the infinity. Generally speaking, center image quality remained more or less consistent throughout the aperture range, with no significant visible different for the supported focusing range. The border image resolution was though noticeably softer at wider apertures and to get a more or less visually uniform quality across the entire frame you'd have to stop down the lens to at least f/4. In many cases,  wide angle lenses show minor degradation in border quality because  of the field curvature, which changes the focusing distance from the film plane to the objects across the picture frame. Carl Zeiss Distagon T* 35mm f/1.4  is not an exception to the rule, as the lens does show some field curvature, but it's quite minimal, which leads me to speculate that floating lens design increases the overall complexity without significant noticeable benefits in resolution. As a matter of fact, the new version of the Distagon T* 35mm f/2 for Nikon and Pentax mounts actually moves away from the floating design, but manages to deliver equal if not better overall resolution..

While border image resolution at f/1.4 is not particularly impressive, many might still consider this to be a no issue at all. After all, the major reason for buying such a fast lens as Carl Zeiss Distagon T* 35m f/1.4 is to benefit from a thin DOF and achieve nice, clean separation between the in-focus and out-of-focus areas. As I have been mentioning in other reviews, the hole topic of bokeh (out of focus area) is rather controversial, with many different variables affecting it. So since all these variables are impossible to account for in a regular field test, the examples below only demonstrate how the lens would work at close to the minimal focusing distances, where the blurring of background is typically the heaviest. The two shots below, both done at ~30cm, show the case.

 

ISO 400, 1/4000, f/1.4, 35mm (Canon 5D)
ISO 400, 1/80, f/8, 35mm (Canon 5D)

 

As expected for an f/1.4 lens, Distagon T* 35mm f/1.4 excells in blurring the background. The depth of field in the left shot (done at f/1.4) is super thin and any detail quickly blends in into a smooth, almost uniform background mask. Small tonality changes in the background disappear completely, and the high contrast transitions actually get smoothed away as well, making the foreground in-focus object stand out very nicely. Note that for some, such a thin DOF might actually be a challenge (I'm in that camp as well), since it really requires you to focus very carefully on the area you actually want to be in-focus. Many camera AF systems would actually lit up an AF confirmation not at a particular distance, but rather thoughout a small range, which could make your picture look front or back focused. Why? A wide range of possible causes - an AF point in most cameras is not a single point, but rather a small area, which can cause the AF system to think it focused where you wanted it to focus, a miscalibrated AF system can or improper adapter (adapter thickness or AF chip itself), etc. When starting with fast alternative manual focus lenses I found myself surprise by how many times my focusing ended up slightly off, so I started using an old trick to minimize the possibility of misfocusing. I'd use focus bracketing while shooting in a burst mode. By varying your focusing ever slightly, you improve your chances of getting at lest one shot done at the right focusing distance. But you do end up with quite a lot of pictures this way, all of which need to be sorted through and majority of them discarded. Trade-offs, trade-offs...

Notice that as you stop down the lens, the DOF area expends (typically equidistantly around the point in focus, with the cut-off at the minimum focusing distance), bringing more and more definition first to close and then far objects. But take a look at the picture on the right side, taken at f/8 - the background is far from being in focus, although obviously you can now at least distinguish various object shapes. The background does not look particularly attractive to me here, but at such a small aperture setting, no lens is likely to produce a smooth background. However, considering that the background still remains blurred when shooting at such close focusing distances, you can safely assume that somewhat wider apertures would give you quite a decent background blur. In the case of Distagon T* 35mm f/1.4, f/2 and even f/2.8 produced quite a decent blur, while giving a somewhat larger DOF that can help you put your subject completely in focus and worry a bit less about super precision focusing.


ISO 100, 1/250, f/1.4, 35mm (Canon 5D)
ISO 100, 1/250, f/1.4, 35mm (Canon 5D)

 

To round up the discussion of DOF, let's take a look at two other properties of the lens, which typically affect the feel of quality of the out of focus area - the OOF highlights and OOF double-edging. Ideally, the lens would evenly lit OOF highlights with neutral or smooth blending around edges. Furthermore, the lens should not produce any double-edging around any OOF objects, whether the objects are in the fore-ground or back-ground. This is actually where Distagon T* 35mm f/1.4 excels - OOF highlights are uniformly lit and blend into background qutie nicely and there is no sign of double-edging at all. Very nice results all in all!

 

ISO 100, 1/1600, f/1.4, 35mm (Canon 5D)
ISO 100, 1/60, f/8, 35mm (Canon 5D)

 

Let's now review some other properties of Contax Carl Zeiss Distagon T* 35mm f/1.4. As can be seen from the shots above, Carl Zeiss Distagon T* 35mm f/1.4 fell prone to some flare in certain, rather extreme. situations. With the sun positioned close to the frame (peaking  over the top of the building from the left hand side), the lens shows some color shift as well as reduced contrast, pretty much throughout the entire aperture range. At smaller apertures, you can also observe aperture ghosting, which is clearly seen in the image on the right hand size (shot at f/8). Is there a reason for panic? Probably not, as long as you either use a lens hood or  compose your images in such a way that the strong light sources don't graze the front element of the lens under directly.

 

Vignetting @ f/1.4 - full frame vs 1.6x crop
Vignetting @ f/1.4 - full frame vs 1.6x crop

 

Carl Zeiss Distagon T 35mm f/1.4 showed moderate amount of vignetting on a full frame body with wide open aperture. Stopping down helps reduce vignetting and Distagon 35mm f/1.4 is no exception here - by f/2.8 vignetting is almost gone. On an APS-C body the lens shows basically no vignetting at all pretty much throughout the aperture range.