Sigma won't resolve incompatible lenses

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<p>Canon does not make Sigma lenses obsolete. Sigma's reverse engineering of the operating code in the lens ROM is at fault.</p>

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<p>Just as a point of order. I am not at all sure of this. Large companies have more than once been found to <em>re</em> -engineer their products to purposely <em>break</em> third-party manufacturer's reverse-engineering. Although seldom publicly acknowledged because of anti-trust/anti-competitive problems, this is fairly common practice in the computer world.</p>

<p>In any case, can you expect a modern electronically-controlled lens to live forever? These Sigmas still work on the cameras that existed at the time they came out and Sigma did support many of these with re-chipping for some period of time. This situation makes me careful about buying ancient EOS-compatible Sigma lenses, but as Kin says, the recent ones seem to work just fine.</p>

<p>Tokina was also known to have issues. Particularly certain versions of the AT-X 28-70/2.6-2.8 had AF issues. There are also others.<br>

As for Tamron, it's been repeatedly denied by both Canon and Tamron that Tamron made a deal with Canon for the AF communication protocol, but that rumor/suspicion persists.</p>

<p>FD lenses did not get "abandoned" by Canon. They were introduced in 1971 and stayed in production for 21 years. That is an incredible life cycle for any product. The FD lenses are superb and Canon kept faith with the lens mount when others were swapping mounts around. <br>

BUT when Canon introduced autofocuse there was no way the FD mount could carry on.<br>

Canon did not have to change the specification when digital came in. Well done Canon.<br>

The earlier EF lenses were slowish to focus and the later ones were a lot faster. I have no problems with any of my EF lenses on my EOS1N (film) or EOS D5 (digital).<br>

The only concession was that APS size sensors could use a less expensive lens so they introduced "S" versions to cut the cost of digital SLRs. But that's an optical issue not a mount issue.<br>

You can get an adpter to fit FD lenses to EOS EF mounts. They have to have a lens multiplier to get the infinity focus onto the film plane, so the focal length gets a bit longer. I have two - one with a lens and one with the lens removed, which I use for close up work.<br>

I cannot see any point in fitting an autofocus lens on a camera without autofocus.<br>

You can buy excellent quality used FD lenses for very low prices too.<br>

Sigma EF lenses are a nightmare - they reverse engineered the system and got it wrong. So it is hit and miss whether a Sigma EF lens will work on a particular EOS camera. I am looking at one on my desk that is little more than a lump of glass and won't couple with any of my EOS digitals or my EOS 1N film camera. I cannot even use it in manual mode.<br>

My Tamron 90mm FD and 90mm EF (probably the best portrait lenses ever) go on anything that's FD or EF respectively. So this is a Sigma thing.<br>

In over 40 years of being a Canon user and with a range of cameras and lenses, I have only had 4 problems:<br>

Once my battery in my T90 was too cold and by the time I had warmed it up I had missed the shot (entirely my fault - I forgot that unlike F1's you have to have a battery).<br>

One of my two T90s (long after their sell-by dates) went wrong (a known fault) and I sold it rather than pay for the fix.<br>

My A1 has a mirror wheeze but it does not affect shutter speed (not bad for its age and more to do with low use in recent years).<br>

My old Sigma EF won't work on anything younger than and EOS 1N.<br>

Where is the downwards compatibiliy from Minolta, Sony, Pentax, Yashika, Chinon, Olympus and all the others who are or were around at the time?</p>