Adding a 2x telephoto conversion lens will double your lens' magnification.
Camera equipment is expensive. Whether you are a professional or an amateur photographer, adding equipment represents an investment. Using specialty devices such as a 2x telephoto lens can extend the range of the lenses you already have in your bag. These lenses cost less than a longer telephoto lens, but they have drawbacks.
Lens Speed
Some lenses are referred to as being as being "fast" lenses. These lenses have a large minimum aperture that allows more light to be transferred through the lens into the camera. When more light travels through the lens, the camera can use a faster shutter speed for the correct exposure. When a 2x telephoto lens is attached, not only does it increase the focal length of the lens by a factor of two, it also increases the minimum aperture by the same factor. If you are using a 200mm f2.0 lens, attaching a 2x telephoto lens gives you a focal length equivalency of 400mm f4.0.
Image Quality
Non-zoom lenses, also known as prime lenses, are known for their sharpness and quality of image reproduction. Depending on the make and quality of the 2x telephoto lens, adding one to your prime lens may cause the image to look softer or slightly out of focus. Lenses are precision items that are constructed for the best possible performance. Adding another set of lens elements for the image to pass through can degrade the quality of the image.
Camera Shake
Telephoto lenses of 300mm or longer are typically used with a monopod or tripod. While these lenses are typically heavier than smaller telephoto lenses, the main reason they are used is because the field of view on these lenses is very small. If the lens is not held completely still during exposure, the image appears blurry as a result of camera shake. Adding a 2x telephoto lens to a 200mm lens creates a 400mm lens; if not held steady during exposure, camera shake will be visible.
Connectivity
Modern digital cameras are as much mini computers as they are cameras. Autofocus lenses communicate with the camera through a series of small electrical contacts on the lens that match with similar contacts on the camera body. If the 2x telephoto converter does not have the same contacts as the camera and lens, you may lose some of the features that communicate through those contacts.
Tags: telephoto lens, 200mm lens, Adding telephoto, camera shake, contacts camera, during exposure
