Like all Contax RTS lenses the 35-135mm feels well built with a nicely dampened focus ring. The focus ring action is light - it is a lighter action than my Contax 100mm F2 Planar. The focus ring feels very smooth and really is a joy to use. The only thing that seems a bit awkward is the secondary focus ring for the macro function. To engage the macro mode, the 35-135mm has to be at 35mm and then the secondary ring pulled towards the camera body. The sliding action can be a bit rough; though, my latest 35-135mm engages the macro mode without much effort at all.

HANDLING

The Contax 35-135mm is rated F3.3 at 35mm and F4.5 at 135mm, but I suspect the lens has a lower T-stop rating. When using the Canon 24-105L (an F4 lens) the viewfinder seems brighter than the Contax 35-135mm. At 135mm the viewfinder is dim and seems more like a F5.6 lens - and so do the resulting shutter speeds. Focusing in dim light levels, such as the last couple hours of daylight, is challenging. With F4.5 there is alot of DOF, so images do not “snap” into focus. If using a tripod and Live View, the keeper rate is good - but that sort of defeats the purpose of a “walk-around” lens. Adding the Canon EC-s focus screen has improved the keeper-rate.

The Contax 35-135mm is a long lens, thus the incoming light has to travel down the full length of the barrel. A long lens barrel means the images are more susceptible to camera shake, thus the one-of-the-focal-length rule for the shutter speed does not work well. Even at 35mm I suggest keeping the shutter speeds at 1/200th or faster - which is difficult with a slow aperture. The lens’ weight further contributes to camera shake risk. With the Canon 1Ds Mark III and its good high ISO performance, bumping ISO to get better shutter speeds goes a long ways towards netting sharp images. Good technique is critical at the telephoto end.

There are an array of lens hood options. Per the Contax specifications, the default is the Contax 82/86s Metal Ring and a Contax #1 Metal Hood. I do not like this combo because it is two pieces. Instead I use a Contax W-1 Metal Hood which works just the same - but is just one piece (less hassle in the field). I have also tried the Contax 82-86 Metal Ring (note - no “S”) and that works as well, but I have noted a trace of light fall off in the extreme corners. My suggestion is the Contax W-1.

LENS PERFORMANCE

Across its entire focal range the Contax 35-135mm is a solid performer. The 35mm side has nice resolution, distortion is well controlled and the images have the typical Zeiss coloring. The corners are pretty good. At F8 the corners are sharp, but the resolution is lower than the center of the lens. Images have a nicely balanced contrast with good shadow detail. There is some barrel distortion which corrects easily is most raw editors. I have not noticed any complex wave distortions like those found in the Contax 21mm Distagon. The wide open rendering at 35mm is pleasing to my eye. At 35mm I feel the resolution is as good or better than the Canon 24-105L at 35mm. The Contax has higher resolution than the 24-105L, but the corners on the Canon 24-105L are better (assuming a F8 image).

The 135mm side is a bit more exciting as the 135mm focal length does offer nice bokeh for portraits. Compared to the Canon 24-105L, the Contax 135mm reach offers more background blurring potential. However, this is no Canon 135L. At 135mm the aperture feels more a F5.6 lens than a F4.5 lens. Bokeh is pleasant in most conditions. Busy backgrounds such as pebbles, rock beds or foliage can create some undesired effects. This true for most lenses, so this is not a demerit solely against the Contax 35-135mm. The Contax 35-135mm can render a pleasing portrait, but for portraits and similar subjects, I rather use the Contax 100mm F2 Planar.