Are canon t70 and canon eos rebel xsi lense compatible?

The short answer is: "No" The long answer is: The T70 uses Canon FD mount lenses. FD lenses can only be focused manually. All of the exposure communication connections between the camera and lens are mechanical. An EF lens will not fit onto an FD body. In 1987, Canon introduced EOS cameras that use EF (electro-focus) lenses. All of the exposure and focusing communication connections between the camera and lens are electrical. An FD lens will not fit directly on to any EOS camera. The Rebel XSi camera is a Canon EOS digital camera that can use EF lenses or the smaller EF-S lenses made for APS-C DSLR's. Adaptors are available on a popular internet auction site that will connect an FD lens to an EOS body. The price in 2008 is just under $40, including shipping. Lens functions are manually adjustable only, and are not very convenient when used in this way.