The Contax camera is complex metal casting body filled with many high precision parts with complex shapes made of various metals. It can be highly susceptible to deterioration of shutter performance in cold weather due to dimensional changes in the metal parts caused by temperature change. All metals change dimension with temperature change. Generally metal pieces become longer when the temperature increases and become smaller when the temperature decreases. The overall situation is very complex inside a Contax when it is exposed to a large temperature change, such as going from inside a nice warm house in winter to the outside where it is close to freezing or below.
Another problem that can really gum up a camera is old lubricant. 50 year old grease tends to become like concrete when it is exposed to temperatures below 45 degrees Fahrenheit. If your camera has not been serviced in a long time and you intend to take it on a winter vacation, a very serious consideration of a complete servicing will doubtless save you much disappointment when you open the processed film envelope. It is also possible the problem may become evident quickly when the camera is exposed to cold air. The wind mechanism may freeze as also may the focusing wheel or the rewind knob. The shutter release may not work. All these things can happen due to old deteriorated lubricant exposed to relatively moderate lower temperatures.
When I open a camera for servicing it is always easy to identify a camera that spent a lot of time going in and out of the house in winter. Screw heads are rusted, internal parts are rusted, brass parts are pitted and rough and it is a real struggle to get the camera to work properly. In many cases it is not possible to restore the high shutter speeds of such a camera. If you live in a cold climate and want your Contax to stay in good shape it is important for you to understand just how damaging condensation of internal moisture can be to your camera. The phenomena of water condensation in the camera is relatively complex, but very important.
The Contax camera body is light tight and therefore relatively air tight; but there is some very slow exchange of air with the outside. If your camera is kept in a nice warm humid house the air inside the camera will also develop the same high relative humidity as the air in the house. When this camera is taken outside in very cold weather the water in the air inside the camera will tend to condense as very small droplets inside the camera mechanisms as the camera begins to cool. This will dry out the air inside the camera. When the camera taken back inside the house, the humidity in the home air will diffuse into the camera due to the difference in the humidity between the home air and the camera internal air. Since the camera is still going to be cold for a while, the water in this new air will also condense. As the camera warms the amount of water in the form of droplets inside the camera will not fully evaporate back into the camera air. The reason for this is that there is more water in the camera now than than there was when the camera was taken out of the house. If the camera is taken in and out of the house over the winter the internal parts can become very corroded due to constant presence of liquid water inside the camera. It takes a very long time for the excess water inside the camera to diffuse out of it.
The solution to the problem is simple. Purchase one of those small catalytic hand warmers at a well equipped sporting goods store and get it nice and warm before you leave the house with your camera. Wear a nice warm coat with an inside pocket that is large enough to hold your camera and the hand warmer. Keep your camera inside the pocket when you're not using it and remove it for only as long as is required to take your pictures, then return it to the warm pocket. Always keep your camera warm.
If you have an old Contax and you want it to be reliable in Winter have it serviced.