Will this extender lenses be compatible with my lenses?

Is this the Canon EF 2x II Extender goal, to be compatible with my Canon 40D, which is a Canon EF 28-135mm f/3.5-5.6 IS lens.

Yes Just remember that there will be a multiplier of 2x with the f-stop too. His 28-135mm lens f3.5/5.6 will be a 56-270mm f7/11.2. So if you're using the 28mm f3.5 and get a shutter speed of 1 / 250 sec. when installing the tele Shutter speed be reduced to 1 / 60 sec. -2 Points. EDIT: Canon's site states the following about the Extender EF 2X: "… offers excellent performance with compatible EF lenses …" It is true that diligently for a letter of support, but you can call Canon Technical Support line.

Canon EF 2x III Extender Lenses Review