I have the venerable, and unique Canon EF 28-300L IS USM super-zoom lens. It seems to be in perfect condition and has been so for some time since I bought it about 10 years ago. Recently, when I began shooting with it using my FF cameras: EOS 5DMkIII, MkIV, 5DsR, and in each case it takes one or two images and displays the dreaded 01 error: Cannot communicate with the lens, clean contact. Because the lens displays the same issue on several cameras, it is logical to assume that the lens has a fault.
So that is what I have done (several times) is clean the sensors on both camera and bodies: they don't seem particularly worn and are bright and shiny.
HOWEVER! If I put the lens on my crop sensor cameras: 60D, 7DI, 7DII, 80D, 90D, M5 (with adapter), and the FF R5 (with adapter) it performs perfectly, working through the various zoom and shutter speed ranges and at high speed continuous shots.
That, I find somewhat confusing. I looked at the contacts and compared them to other lenses, and there are exactly the same number of contacts and in similar condition, yet they work fine!
I am throwing this out there to the brains trust and any Sherlock Holmes!!!
I have no knowledge of that lens, or even the EF system particularly... so take this with a grain of salt. However, I have worked on tech devices for 40 years or so.
When you are communicating with some device -- such as the computer inside the lens -- you can detect that something has gone wrong. In that case, you try to guide the user to fix it themselves by suggesting the most likely cause. In this case, that would be dirty contacts. In other words, "dirty contacts" isn't an actual diagnosed problem, it's just the suggestion that's most likely to be of use to a typical user. I.e. a guess.
In your case, it looks to me like something has gone wrong inside the lens -- maybe a bad solder joint. Thermal cycling over years, slight vibration, etc., might have just got it to the point where it's come loose.
As for why it works on crop cameras -- yes, the contacts are the same, but they might be used differently on those cameras. Maybe some contacts aren't used at all. I dunno, like I said I don't know EF. But I can basically guarantee that what's going on behind the scenes is more complicated than you would think -- because it always is.
Anyhow, sadly, I think your lens needs repair. Best of luck, and I hope this has provided some illumination.
Thanks for your input, Atticus. What puzzles me is that it works with the R-bodies via the adapter. It even works with the FF EF bodies, but only for a few shots, and then it gives the error message, so there is a circuit connection. Logically one would expect that those RF cameras would use the same circuits as the EF units, but in that case they show no errors.
Absolutely, sending it in might be an idea, but I suspect that the lens will not be serviced as it is a vintage 2004 unit. Well past the normal servicing envelope.
That said, it works perfectly with the various crop bodies: EF-S and EF-M alike and with the RF mount, so even if I can't get it serviced, I can still use it and the good news is that it works with the newest tech. I don't use this lens a lot, so it's not mission critical but it is a challenge...
"But I can basically guarantee that what's going on behind the scenes is more complicated than you would think -- because it always is."
I would have to disagree with that. Not always anyhow. Plus it is always, always, best to eliminate the simple or easy things first.
Well, I'm afraid I have to disagree with your disagreement. After a lifetime spent developing tech products (phones, tablets, netbooks, etc.) I can absolutely tell you that products like that are always more complicated than an outside user would think.
Of course it's always sensible to eliminate the simple options first. I certainly would have started by cleaning the contacts (if they looked dirty). But if you start wondering about why something happens in one situation but not another, just know that the internals of these devices can be way more insane than you might imagine. You might think, for example, that the EF communications protocol is one, simple protocol; but given all the changes that have happened over the years, I would bet that it isn't. I wouldn't be surprised at all if a lens used completely different communications methods depending on what camera it's attached to. Like, for example, SD cards do.
"Of course it's always sensible to eliminate the simple options first."
What's the point if it is always the most difficult complicated thing . You may as well skip the easy stuff if it can't be that simple. In reality it can be that simple and often times it is a simple thing. And guess what Canon service will know.
I think you misunderstood my post. I'm saying that technology products are always more complex than they seem. This was in response to Trevor wondering why his issue happens on some cameras and not others.
I'm not saying that any given problem is "always the most difficult complicated thing". In fact it almost certainly isn't. It's often going to be something pretty simple. And the most difficult complicated thing is pretty horrific.
Sorry to not be of any help. Actually I had one of them a long time ago. I didn't keep it long. I'll keep my opinion about it to myself for now. Actually I did not know it was still in production or available. It does need to go to Canon for service.