Use of teleconverters

I am using a Canon EOS 5D II camera and have a 75-300, 4-5.6 tele zoom lens. Considering a teleconverter to increase range. Can any one advise as to the performance of 2X/1.4X teleconverters of Canon or Kenko make? Especially from the point of auto/manual focusing and image sharpness?

At its long end your lens would become an F/8 or F/11 lens, if you use a 1.4 or 2.0 TC. Since AF only works reliably for apertures above F/5.6, you would be confined to manual focus. In addition, the view finder of your camera will be quite dark and the IQ significantly compromised. I routinely use a 1.7 TC on a 70-200 F/2.8 zoom lens. Even with this fast lens I have to stop down from F/4.8 to F/5.6 and keep the zoom below about 180mm in order to maintain IQ.

My advice is not to use a TC with your present lens.

One other point; Canon teleconverters can only be used with certain Canon lenses, due to their design. I am not sure, without looking it up, but I suspect your lens is one that will not fit.

Teleconverters only work well with top quality lenses; mostly primes and a few zooms. I did try using a Canon 1.4x with my Canon 70-300 lens by inserting a 12mm extension tube between the converter and lens to try to create a better macro lens. But the results were disappointing, although using a 25 mm extension tube did give me closer macro focusing.

Geoff is correct, they only work on select lenses. Any Prime lens 135mm or larger, and a few of the large L zooms. (70-200......100-400.......maybe 28-300).There is a list of lenses on the canon site.

Canon teleconverters won't work with a 75-300/4-5.6. I'm not sure about the Kenko, but I doubt you'd like the image quality. Time to open the wallet I'm afraid :(

What the previous three posters said. I asked the same question of Canon Tech Support a few months back and their response was the same - the Canon teleconverters will not work with the 70-300.

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Originally Posted by GiantTristan

At its long end your lens would become an F/8 or F/11 lens, if you use a 1.4 or 2.0 TC. Since AF only works reliably for apertures above F/5.6, you would be confined to manual focus. In addition, the view finder of your camera will be quite dark and the IQ significantly compromised. I routinely use a 1.7 TC on a 70-200 F/2.8 zoom lens. Even with this fast lens I have to stop down from F/4.8 to F/5.6 and keep the zoom below about 180mm in order to maintain IQ.

My advice is not to use a TC with your present lens.

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Hi All
Sorry if this post drags this one slightly off topic, but I'd be most interested if the same comment - or similar applies to the Nikon VR lenses. We use a 70-200 VR1 for motorsport and often lose shots in the middle of a sequence, sometimes alternate shots and it's most annoying. That said we usually shoot at f2.8 for light and for DOF to isolate subject & background. Maybe need to increase ISO / pan with lower shutter speed and decrease aperture??
Any info / comments really appreciated as this is most frustrating.
Rob