Zeiss Vario-Sonnar T* 24-85mm f/3.5-4.5 N (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 Carl-Zeiss Vario-Sonnar T* 24-85mm f/3.5-4.5 is the 2nd converted Contax N lens for Canon EOS tested here in OpticalLimits. 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. The lens is a bit slower than f/4.5 @ 85mm and interestingly it is recognized as 86mm f/5 in EOS land here.

The Zeiss 24-85mm was the standard "kit" lens sold with the Contax N1 and Contax N Digital. Naturally this didn't translate to "cheap" regarding the high-end target market although it was a relatively affordable item by the Zeiss standards of the time. It was also the first N-mount lens to feature an ultrasonic AF drive.

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.

Typical for most Zeiss lenses the build quality is very good thanks to high quality materials. However, the lens uses a dual-cam design - two inner lens tubes extend when zooming towards the long end of the zoom range - and this sets limits to the build tolerances. Unfortunately the lens seems to suck in lots of air ... and dust. Used samples are never in perfectly mint condition in this respect. 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. You may notice that the EOS 350D looks rather dwarfish in comparison - it is a relatively short but "fat" lens thanks to the big front elements and the huge 82mm filter thread.

As mentioned the Zeiss features an ultrasonic AF motor including FTM (full-time manual control in one-shot AF mode). It's not a speed daemon but reasonably fast and relatively accurate. 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 length38-136 mm (full format equivalent)
Equiv. aperturef/5.6-f/7.2 (full format equivalent, in terms of depth-of-field)
Optical construction14 elements in 12 groups inc. 2x fluor crown and 2x aspherical elements
Number of aperture blades7
min. focus distance0.5 m (max. magnification ratio 1:6.7 @ 85mm)
Dimensions90 x 71 mm
Weight570 g
Filter size82 mm (non-rotating)
Hoodsupplied, petal shaped (snap-on)
Other features-

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