Extension Tubes???

[dicklaxt]

Just exactly what are "Extension Tubes" and when are they used and why?

dick

[coffee]

Extentions tubes are used when you want to add reach to your lens. But it comes at a cost of ambient light. I can turn my 100-400L 4.5/5.6 lens into a 140-560L with the use of my 1.4X Kenko extention, but with the sacrafice of one full stop. So now my max F stop on that lens is 5.6/8.

[ca7696]

so are extension tubes the same as teleconverters??(TC's)