Long telephoto lenses are expensive.  And yet, there is an inexpensive solution to extending a lens' focal length, the use of a tele-converter.  Yet, the common wisdom is that tele-converters result in significant picture deterioration, especially low-cost converters, and especially if combined with low-cost lenses.

So how bad are the results?  I tried to find out by pushing the limits of "extreme tele".  The following photos were taken with extreme telephoto lens "arrangements", shot with an old Yashica TL Electro (fastest shutter speed 1/1000s).  I created focal lengths between 600mm (3 x 200) and 3000mm (2x 3x 500mm).   The 2x or 3x converters extend the focal length by that ratio (e.g., 200mm  x 2 = 400mm), but also reduce the light intake accordingly.  For example, the 2x converter reduces a 2.8 aperture to 5.6, the 3x converter to 8.  This produces a double-difficulty.  After all, as the focal length is extended, the shutter speed needs to be reduced in order to create a steady (sharp) image.  At the same time, the aperture goes down.  Hence, one has to do one or more of the following: use a higher speed film (e.g., Fuji 800), take pictures under very good light conditions, or use a tripod.  Also, always over-expose, especially when using more than one tele-converter.

Example: The shortest focal length in the samples is 600mm (3x 200mm).  For 600mm, I used an inexpensive Vivitar lens (200/3.5), and a similarly inexpensive Vivitar 3x converter.  The result was astonishingly good (better than the scan suggests).  By choosing a high shutter speed (e.g., 1/1000s) the lens can still be hand-held.

Example: The longest focal length I shot was 2 x 3 x 500mm = 3m!  The lens was a simple Samyang (?) 500/8 lens.  This picture was taken from several hundred yards away.  It is underexposed because the lens system absorbs so much light. 

Example: This photo was (obviously) taken at night and with a tripod (ca. 30s exposure).  The red lines are the tail lights of cars driving by on the highway.  Focal length was 1.5m.