Carl Zeiss Distagon T* 25 mm f/2.0 ZE/ZF.2
3. Build quality
In the photo below the Carl Zeiss Distagon T* 25 mm f/2.0 ZE is positioned next to the manual Samyang 24 mm f/1.4 ED AS UMC and the Sigma 30 mm f/1.4 EX HSM for smaller detectors.
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The whole casing of the tested lens is made of solid metal with particular parts fitting each other perfectly. When it comes to the mechanics it is a device of the highest quality - there is really nothing to carp about. When you hold this lens in your hand you don’t doubt it can function many years without any problems.
The Distagon starts with a metal mount with contacts so the lens can communicate with a body, transferring such information as focal length and aperture values. The aperture can be adjusted every 0.3 EV step. The mount surrounds a rear element of the lens, 24 mm in diameter, which moves slightly during focusing. When you set the focus at infinity the rear element is situated the closest to the mount; at minimum focus it is hidden about 0.5 of a centimeter inside the casing. The front element remains immobile at the same time which means that during focusing optical elements just change their mutual positions.
A depth of field scale is the first element of the casing which sticks out. It features markings for f/22, f/16, f/11, f/8, f/5.6, f/4 and f/2.8 aperture values (but markings for f/11. f/5.6 and f/2.8 are not signed). Opposite to that scale there is information that the device was made in Japan.
A manual focus ring is the next part of the casing. It is as wide as 39 mm and most of it is taken by metal ribbing under which you get a distance scale expressed in inches, feet and meters. The ring is noticeably well-damped but it moves smoothly and very steadily, allowing you very precise settings. Here everything is exactly as it should be in a high quality manual instrument. Running through the whole distance scale needs a turn through about 115 degrees.
The lens ends with a silver ring with a hood mount. On the outside the ring features a non-rotating filter thread, 67 mm in diameter. The front element is surrounded by a part of the casing on which there is the name of the lens and its parameters. As we’ve already mentioned the front element is immobile and its diameter is about 4 cm.
When it comes to optics the lens consists of 11 elements positioned in 10 groups. As you can see in the diagram below the second element was made of special glass with anomalous partial dispersion and the penultimate element is aspherical in shape. Inside the lens you can also find a circular aperture with nine diaphragm blades which can be closed down to the value of f/22. As the name of the lens indicates, all air-to-glass surfaces are covered by high quality T* anti-reflective coatings which are supposed to ensure high transmission, great colour rendering and block out any flares.
Buyers get both caps and a petal-type hood in the set. The hood is made of metal which was darkened and padded with black velvet on the inside. It is a pity, though, that for such a price you don’t get any case as well.