Canon 50D and Canon 100-400mm Issues

<p>I have an interesting challenge that has come up recently on the combination of my 50D and a 100-400mm Canon lens. They work fine together for a few shots, and then I get either an error 99 (generic, I know), or the camera just freezes up - it's almost as if the mirror locks but the shutter won't fire. I can clear it by removing the battery, or as I discovered over the weekend just changing the mode button (e.g. from P to TV or vice versa) frees up the shutter. I've cleaned the contacts without any obvious improvement in the situation.</p>

<p>Here's where it gets odd. Any other lens on the 50D works fine. The 100-400 on either our 7D, or an older Rebel body works fine. It's just that combination of the 50D and the lens that creates this problem. Now, the 50D is on its last legs, I was planning to do something about it next spring before the racing season gets going. And the work-around of switching the mode button is OK for now - I can work with that. But does anyone have any other thoughts about this? The biggest worry is that maybe there's something wrong with the lens, but I'm not sure what that would be.</p>

<p>My first guess would be a loose connection, which, I would guess, based on your description is on the 50D's end. The contact pins can bind (passing through the plastic retainer), and give an intermittent contact. I would try to see if you can find (by fiddling with the pins) if any feel loose, or improperly sprung, or maybe bind a smidge?</p>

<p>Alternatively, the loose contact <em>could</em> be within the lens, though it seems less likely, and the different mounts bind slightly differently with difference in mount tightness. If you noticed a significant difference in how easily the lens mounts on the 50D vs. your other cameras, I'd guess that was more likely.</p>

<p> </p>

<p>David, I had a similar experience, which I posted previously, in terms of the presenting fault,with an old D30 body acquired cheap second-hand. I'm told that the error message, with the mirror locking up and the shutter failing to fire can be caused by a malfunction of a sensor that determines that the mirror is fully "up" before the shutter is activated. The fault in my case was similarly intermittant, but not related to any one lens. If this is the same problem then I fail to see how the lens can be a contributing cause - unless for some reason, it's interupting the travel of the mirror (which I guess is fairly unlikely). My body now best serves as an ornamental "doorstop".<br>

Tony Buckwell </p>

<p>Thanks Marcus - I'll check on the mounting ease, and also on the mounting pins. It is quite conceivable that the combination of pins on that camera and lens creates a unique situation.</p>

<p>Tony - I'm hoping that the body gets me through the fall, but I'll definitely carry a back-up for anything important. I doubt that lens is interrupting travel of the mirror since it works initially for multiple shots, so I'm guessing (and kind of hoping) that its the body, not the lens. I appreciate the help.</p>

<p>It's odd that the error is 99, rather than 01, which is more typical for lens problems.</p>

<p>The best error 99 troubleshooting guide that I'm aware of is at lensrentals.com,</p>

<p><a href="http://www.lensrentals.com/blog/2008/12/canons-error-99-the-man-the-myth">http://www.lensrentals.com/blog/2008/12/canons-error-99-the-man-the-myth</a></p>

<p>It's six pages long and quite complete.</p>

<p>You might try turning off the AF and image stabilizer to see if that makes a difference. Also shoot with the lens wide open so the aperture doesn't have to move. And if your batteries are old, that could be contributing.</p>

<p>Thanks Alan - some more things to try. I'm beginning to believe that part of the solution involves an offering of dead chickens and chanting...</p>

<p>You could also try the old pencil eraser method of cleaning the contacts on both lens and body...you never know. </p>

<p>I had this problem and changing the silver coin battery for a new one ...</p>

<p>That's an interesting idea Jose - that worked for you? I haven't done that since I got the camera back in 2009.</p>