In article , rainer@u.washington.edu says...

>What is the best way to get closer than my lens can handle? Should I go
>for an extension tube or close-up filters? Would a teleconverter work
>at all? What are the trade-offs between the three and what are effects on
>image quality and light?

This is not as easy to answer as it might appear, since particular lenses
perform better with one (or a combination) solution than another (though
I would eliminate single-element close-up lenses, and substitute 2-element
achromats made by Sigma, Nikon, Canon, Minolta, Leitz, and probably others).
In general, if the lens has a simple or symmetrical optical design, it may
work well with extension tubes. If it is complex and non-symmetrical, I would
try an achromat. In both cases, I would stop down to at least f8 (preferably f11 or 16, but no smaller if using tubes...). Converters work well with many moderately-wide to moderately-long lenses to provide greater magnification (these also require stopping down for good performance - especially with 2X converters). BTW, converters can be combined with tubes and/or achromats to increase magnification - and the results can be quite sharp around f11-16
with some lenses. There is no light loss when using achromats/closeup-lenses, one stop loss with 1.4X converters, 2 stops loss with 2X converters, and some loss with tubes (2 stops at 1:1). BTW, Vivitar makes an excellent 2X
converter combined with a variable extension tube. Throw a good achromat
on the front, set f11 1/2 on the lens, use a good tripod or flash, and
choose a compatible lens to put in the middle, and you can do high-quality high-magnification macro work. For some samples of bugs (many at 2-3X magnification), go to my web page to "Phun Fotoz", then to "Bugs"...
Hope This Helps
(David Ruether - http://www.fcinet.com/ruether )