This article was updated in April of 2009 after Mark at Precision Camera, our favorite repair shop, provided us with some additional information.

This is probably the most boring article I’ve written for LensRentals. (Personally, I like Smashed Front Element the best.) But, I love a good mystery, and I love debunking dSLR “urban legends”. Every so often I run across an online forum where someone makes broad statements about Error 99 which I know are incorrect or at least incomplete. As is my practice, I’ve boldly charged into these online gunfights devoid of intellectual ammunition (i.e. facts). And predictably, the intellectual level of the discussions quickly spirals down from “Is not”, “Is so” into the traditional online-forum sign-offs of “You get Err99 because you’re a bad photographer” and “if you’ve never gotten Err99 you’re obviously not taking many pictures”.

Because Canon Corporate apparently believes that releasing no information about a problem makes it go away, there is little factual information to debunk the online myths regarding Err99 unless you really do a lot of digging. Googling Err99, Canon EOS error codes, etc. brings up several dozen pages of links most of which are the above mentioned “discussions”. There are a few nuggets of truth out there, though. The most complete of these is a multi-year 2,300 post discussion of Err99 problems at Richard’s Notes. There are also a few thoughtful and factual discussions that have taken place in some of the better forums online. After spending far more hours than I intended looking through these sources to settle an online debate, I thought I’d write a summary of what I found and what we’ve experienced here— LensRentals has over 700 Canon lenses and over 50 Canon bodies (as of December 2008), so we have a bit of Err99 experience.

The Myths

Some of the most common Err99 myths are listed below. Strictly speaking, they are not myths; almost every one is true. The myth part comes from thinking that any one of them is actually the cause of Err99. So:

• Err99 results from an electronic communication problem between the lens and the camera.
• Err99 results from using third-party (i.e. Sigma, Tamron, Tokina) lenses.
• Err99 means that electronic circuitry in the lens has failed.
• Err99 means that electronic circuitry in the camera has failed.
• Err99 results from using third party batteries.
• Err99 is a firmware issue, and can be fixed by upgrading to the latest firmware.
• Err99 started with Canon XT and 20D cameras.

There are a lot more. Almost all of them are true for at least some cases of Err99. The best myth, though, is that Canon purposely created error 99 to prevent the use of third party lenses. As best I can tell, that one isn’t really true, but it does make fun speculation. And, of course, Canon’s nearly total silence on error 99 and other problems certainly helps feed the conspiracy theorists among us.