You cannot use canon digital lenses on a 35mm film camera or on a digital with a full size sensor (eos 1D or 5D).
The standard canon EOS lens is known as an EF lens and will have a red locator dot on the mount, these lenses can be used on either 35mm or digital but when used on a digital with a APC sized sensor you will get the 1.6x focal length issue. Canon digital lenses are known as EFS lenses and have a white locator dot on the mount. These lenses work as expected on a digital body with the smaller APC sensor and do not have the 1.6x focal length factor. These lenses cannot be mounted on a 35mm camera or a full size digital due to the clearance between the back of the lens and the mirror.
If you spend any real money on glass then get the EF series, they are higher quality, there is far more choice and you can use them on all cameras. It looks as if canon will gradually move to full size sensors making EFS lenses useless. The only EFS lens I have is the one that came with the Rebel when I bought it.
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