No it shouldn't, the only way that you could get a picture on the LCD would be if the mirror that allows you to see through the lens was raised and that only happens when you press the shutter release all the way down. There were, I believe, a couple of digtal SLRs with semi-silvered mirrors that would show an image on the LCD prior to capture but I don't believe any are still in production. If the manual for the 400d is anything like the 30d then it should say something in the description of the LCD monitor.