05-15-2014 12:44 AM
That is bizarre. You may want to call Canon support to inquire about that. You've done a good job pin-pointing the issue. The Sun does put out nearly as much energy in infrared as it does in visible... but I would have expected the camera sensor wanted to see a very specific sequence of IR pulses... not just IR wavelengths in general.
While I don't often enable the IR sensor ... I don't recall the sunlight being an issue on my 5D III.
05-15-2014 01:25 AM
I've never enabled the IR sensor!
You mentioned that you use the 2 second delay mode. That mode also enables the IR sensor. Any of the "delay" modes enable the IR sensor. If you look at either the 10-sec or 2-sec timer options they have a symbol of the IR remote next to them.
If you use the 2 sec. delay mode to allow the camera vibration to settle down when shooting with a tripod then this also enables the IR sensor. If you use a "wired" remote shutter release you can use the instant mode (since using pressing the shutter button on a wired shutter release wont shake the camera.)
05-15-2014 05:35 PM
That explalins why the IR sensor would be enabled. However, I have used a wired shutter release before and the camera shutter fired on its own using it, as well. At the time, I thought the problem was the cable remote (which was brand new and Canon brand), but this problem with the 2-second timer and IR sensor would seem to indicate the two conditions are related. I'm relatively certain I would not have been using the self-timer with the cable remote. As you said, it wouldn't make sense.
Does using Live View have any connection with the IR sensor? Chances are fairly good that I switched to Live View in all circumstances before tripping the shutter, whether using the cable remote or the self-timer.
In any event, this certainly can't be normal behavior. I know I'm not the only 5D III owner who uses the 2-second timer on a tripod in the sun!