4th July 2005, 11:11 AM
4th July 2005, 01:35 PM
Canon EOS cameras communicate with EF lenses electronically, i.e. there are no physical coupling to control aperture of the lens, etc. So everything depends on the correct communication between the lens and the camera body.
In the case of 3rd-party lenses (most notably Sigma lenses), they build and programme their lenses by reverse-engineering the communication protocol of original Canon lenses. This is because Canon does not release the full specifications of the EF lens communication protocol to outside companies (= proprietary; closed source). This means that Sigma "guesses" how the camera and the lens communicate with each other, which means it's not 100% accurate.
As with software, the communication protocol can be changed/upgraded and therefore 3rd-party manufactureres will always play the "catching-up" game. Technically this will mean that older Canon EF lenses also may fall into incompatibility, but since Canon are the ones who designed/programme their own lenses, any upgrades to the communication protocol can be made so that the older lenses are still compatible. However, since 3rd-party lenses are not 100% the same bit-wise, they are more likely to fall victim into compatibility traps.
Why it fails exactly falls into the scope of the lens manufacturer's engineering department, so you'll need to ask them why the lens fail at certain apertures, etc.
Although it is possible that newer lenses are not compatible with older bodies, is it not as likely compared to the reverse because newer lenses would have been programmed to accept older bodies/protocols as well.
It is not a EOS 30/33 (Elan 7E/7) specific problem; it can very well occur with other (newer) bodies as well. I too encoutered such a problem - Err 99 -with a EOS 300D and an older Sigma 70-300mm f/4-5.6 (non-APO) lens.
The only way to solve such problems (less buying a new lens altogether) would be to ask the lens manufacturer to "re-chip" your lens. They may do it for free (under warranty or out of goodwill), but if the lens is really very old, they may not be able to do it for you at all since it may not be economically feasible to reprogramme an old lens--and you'll end up having a very heavy paperweight.
Last edited by Ah Pao; 4th July 2005 at 01:37 PM.
4th July 2005, 06:11 PM