First mistake (well maybe)

I unmounted my 75-300 and put on the 28-135, all without thinking that the camera was on! Now I'm all worried that something is not working right..
Does anybody know if the camera should've been turned off when lenses were un'screwed'? Or am I 'screwed'? (Nothing in the manuals mentions anything of the sort anyways.)

You should be fine... I always switch lenses with it on.

I have a Canon film SLR (T90) that I've NEVER turned off (except for battery changes) since I bought it about 10 years ago. Of course, that's a different lens mount, but basically, don't worry about it. They expected that when they designed it.

I think it would be slightly safer to switch off the camera before swapping lenses. However, I have swapped many times without that precaution, and I haven't seen a problem.

I also try to switch off the camera before swapping CF cards. Probably 99% chance that this has no effect, but the camera is so expensive I kind of hate to leave everything to chance.

---Bob Gross---

mcouper:
Don't worry. Canon recommends to NOT to switch lenses with the camera on (at least in my EOS 5 manual), but I've never had a problem and I've forgotten to switch it off a LOT of times

Nothing to worry about, although I wouldn't make a habit of it. I believe Canon recommends turning the camera off first because the image sensor has a slight static charge while on which can attract dust.

Well, on another note. I somehow opened my CF card door while the camera was on and nothing happened. I closed the door turned off the camera and turned it back on again, no problems...

I won't be trying it again.

NiL,

I have done both dozens of times.

Here are the issues with both "mistakes"

1. Swapping lenses with the Camera on:

THE GOOD: This won't hurt the camera.

THE BAD: There is a reason NOT to do this though. With the camera powered up,. the CMOS is charged,. and the static will make it more likely to attract any dust that may happen into the open lens mount.

BOTTOM LINE: Don't fret if you forget,. but do try not to

2. Opening CF Dor with Camera on

THE GOOD: This probablywon't hurt the camera.

THE BAD: If you do this while the Camera is WRITING to the CF card YOU WILL LOOSE IMAGES,.. you may lock up the camera,. and may damage the CF. (unlikely)

BOTTOM LINE: Try to avoid this one!
DO NOT open the CF Door while the Camera is writing to the card! This would be bad

re: one thing not to do

even tho this happened on a Casio slim camera the guy had for 30 mins.

take a photo while opening the battery door, the camera now comes up with System Error and has to back to Casio for repair.

Well this happened to today, with a work mates new camera, just my luck.

I am a good chap however I did offer to pay for the repair if there is any.

The best thing to do with a camera, don't be in so much of a hurry with the dam thing.

Should cause no damage to camera, but with my D60 I have lost a few images because of leaving the camera on when I switched lenses. Have not experienced same with 10D, but then I am much better about switching lenses with camera off. Only happened occasionally in any case.