Zeiss Vario-Sonnar T* 70-300mm f/4-5.6 (Contax N to Canon EF) - Review / Test Report
Lens Reviews - Canon EOS (APS-C)

Review by Klaus Schroiff, published December 2007

Lens kindly provided for testing purposes by Markus Stamm!


The Zeiss Vario-Sonnar T* 70-300mm f/4-5.6 is another converted Contax N lens for Canon EOS. The mount conversion can be ordered via Conurus. It is not a cheap procedure but thereafter the lens behaves like a native Canon EF lens including AF, a camera-controlled aperture and (mostly) valid EXIF data.

A rather slow-speed 70-300mm f/4-5.6 may sound like a relatively affordable tele-zoom but till the end of the Contax-N system it was actually a very expensive lens (~1000EUR) and it's not much cheaper on the used market today.

As usual we'll have a look how it performs on an APS-C DSLR (EOS 350D). I'm aware that some of you may have wished a test on a full format DSLR but these tests will start based on the successor of the EOS 5D.

It is a rather massive and heavy (1070g) lens for its class but the build quality is accordingly high due to high grade materials (mostly metal). The build tolerances are surprisingly tight despite the dual-cam design - two inner lens tubes extend when zooming towards the long end of the zoom range. Unfortunately the lens seems to suck in lots of air and dust. Thanks to an internal focusing (IF) mechanism the physical length remains constant during focusing (but not during zooming). The zoom ring operates a little stiff. Manual focusing feels smooth but it is a rather imperfect implementation because the mechanism doesn't interlock instantly.

The Zeiss 70-300mm features an ultrasonic AF motor including FTM (full-time manual control in one-shot AF mode). The AF speed is fairly slow but the AF accuracy is pretty decent even on the (generally rather unsure) EOS 350D. Besides the mount conversion Conurus faced one little obstacle - Contax N lenses have no AF/MF switch (selected on the camera). However, he found a workaround for this: you have to set the (otherwise useless) aperture ring to the smallest aperture for manual focusing. This may be an unusual thought but it works just fine. Interestingly the new firmware (v2.+) has a new "AF micro-adjustment" feature - similar to the new EOS 1D III it is possibly to do a focus fine-tuning so if you're experiencing a front/backfocus problem you can easily correct this yourself (regardless of the camera model).

Equiv. focal length112-480 mm (full format equivalent)
Equiv. aperturef/6.4-f/9 (full format equivalent, in terms of depth-of-field)
Optical construction14 elements in 12 groups inc. ?x fluor crown elements
Number of aperture blades7
min. focus distance1.5 m (max. magnification ratio 1:4.2 @ 300 mm)
Dimensions88 x 129 mm
Weight1070 g
Filter size52 mm (non-rotating)
Hoodmetal, barrel shaped (snap-on)
Other featuresmacro mode (min. focus=1m)