Almost new Canon 2x Tele-extender version II ... plus used 50mm F/1.4 - $350
Less than six months ago, I picked up a couple of Canon 2x (version II) tele-extenders. I had this idea that I could stack 'em with a 70-200/2.8 and get a 140-800/F11. While this does work (see testing with BuzzLightYear at http://www.komar.org/faq/camera/canon-70-200-2.8is-version2/canon-2x-teleconverter/ ), there are enough limitations that I rarely use it in actual practice ... so I'm selling one of the 2X tele-extenders.
These allow you to double the focal length for more reach by simply attaching these between the camera body and the lens. However, you don't get something for nothing, and as expected, you lose two stops of light - i.e. your 300/2.8 becomes a 600/5.6. Plus the AF speed is slower, and there is a slight degradation in image quality (although much less than cropping a non-TC'd image) and I'm quite comfortable shooting with a single 2x on my 70-200 lens and the additional reach is very, very helpful - check out the sample picture below of an ultimate frisbee pull shot from the far end zone. Another interesting benefit is the minimum focusing distance remains the same, so you can use get lot more detail on close-in items - see the Hummingbird picture below.
The 2x tele-extender work with most telephoto lens (chart at http://www.bhphotovideo.com/FrameWork/charts/canon2xExtender.html ) but be aware that you need to have the aperture within the range of the camera (F/8 for 1-series, F/5.6 for others) for the auto-focus to work ... although you can use LiveView for AF no matter what the aperture.
The 2x tele-extender sell new for about $300 (plus shipping/tax) and mine is still under Canon warranty. It's basically like-new and works great - I just don't need two of them.
Plus ... I have a used 50mm/F1.4 that has just been collecting dust so I'll toss that in for 'ya. These also sell for $300 new, but full disclosure that is front-focuses on my Canon 7D body, so I've had to dial in a "-15" on the microfocus adjustment. I have a 17-55/2.8 lens, and I'm just a "zoom guy" who never uses the 50/F1.4 prime, although the wide-open F/1.4 aperture can be used for some very interesting artistic effects and subject isolation (with blurred background) due to the narrow depth of field ... plus you can shoot in almost total darkness.
I've priced the combo at $350 because it's easier to sell as a single transaction rather than deal with twice as many wanna-be-buyers on Craigslist. If you want one of 'em, $250 for the 2x tele-extender and $200 for the 50/1.4. Cash only and serious buyers only - please don't waste my time and yours - the items are exactly as described and in fine working condition.
2X Tele-extender with original box, pouch, and end-caps - click for hi-res original
Canon 7D with 70-200 at full tele shot for 200mm - click to see full res
Same distance adding the 2x tele-extender for 400mm for more reach - click to see full-res
Adding the 2x tele-extender for more reach is very useful when you are shooting from the far end zone
Shot with 70-200 plus 2x TC - more frisbee pictures with 2x TC
The Minimum Focusing Distance doesn't change with the 2x tele-extender, so you double your pixels on target for closeups
More Baby Hummingbird Pictures
50mm F/1.4 lens - click to see full-res
With the F/1.4 aperture, you can get incredibly narrow depth of field for artistic effects
Plus shoot in very, very low light - click to see full-res
50mm shoots "landscape" photo - much closer that 200/400mm pictures above - click to see full-res
