JimRPhoto wrote:
Have both and it is worth it. Another person showed some comparison photos using an extender, vs. just a longer lens. I could not see the difference. But, as another person said, be sure it is compatible. The 1.4 Canon extender I have will work only with this particular L series lens (of the several Canon L series lenses that I have). JimR
The OP asked about an extender paired with a 70-200 L. This lens is compatible with all of the Canon extenders.