which TC - extension tubes please

[stewsmith]

Does anyone have an idea what extension tube or tele convertor is compatible with the Canon 70-300mm DO IS USM http://www.canon.co.uk/For_Home/Product_Finder/Cameras/EF_Lenses/Zoom_Lenses/EF_70-300mm_f_f4.5-5.6_DO_IS_USM/index.asp

I have emailed a couple of online stores but have had no response.

I already own this lens and love it, but want to add something to it to give me a bit more length.

Stew

[EdBray]

To gain extra length you need a Teleconverter, but with your camera and that lens you will lose autofocus with their use, you will also lose some IQ not as much with a 1.4x converter but a lot with a 2x converter.

You also lose 1 stop of light with the 1.4x and 2 stops with the 2x which will make the view through the viewfinder very dark.

The Canon and Sigma converters will not work with your lens so you would be looking at the Teleplus or Kenko ranges really.

Extension tubes change the minimum focussing distance which give more magnification of close subjects but prevent the lens focussing at infinity.

[coldpenguin]

I have the non-DO version. That isn't meant to work with TC's either, but it does work with the Tamron.
You can auto-focus with the non-DO on the tamron (but a bit slower), on a 400d, not sure whether yours will, or will on a 5d.

[stewsmith]

excellent replies, thank you for your time.

Stew