I am going to purchase a Canon Rebel T3i camera.

[jpalmer]

I have an existing Quantaray 70-300mm lense. Should it be compatible with this camera?

[cicopo]

The exact model would help. What camera were you using it on up until now? Does it auto focus or is it a manual focus lens?

[Samsen]

 Quantaray 70-300mm lense that is actually made by Tameron is a zoom that has been made both for manual FD mount long back also for AF EOS EF mounts. Lens is also made with rebrand ring for many department stores and likewise.

The older manual focusing one will not seat directly on any DSLR unless you use a FD to EOS adapter that adds a bad lens distortion due to cheap interal glass of adapter that is needed to focus to infinity. If you have an older manual Nikon, olympus or pentax version of this lens, you are more lucky as you can use a non glass adapter that will allow use of lens on your DSLR EOS Canons in AV or Manual mode.

I am not so sure about it EF AF version but from other camera copies of this lens, I know that focusing is very slow compare to any Canon lens.

As for image quality; Its really good. Older vesion used to give quit a sharp and nice image if you know how to handle manual focusing, manual metering etc.

In short and if you care to listen to my advise; Just sell it on ebay / amazon or likewise and buy yourself a Canon EF  75-300mm f/4-5.6 III USM that should cost you just above $100.

[ScottyP]

Don't bother.  As digital cameras have inccreased their sensor resolution, lenses have had to be improved to keep up.  The very few lenses left that were designed in the 1990's are almost all replaced by better-resolution versions.  A computer monitor with ability to zoom in 100% or 1000% is just much more demanding than an old film developer on 8 x 10 ever was.

Buy youself a used digital-era lens if you want that range.