I have a Canon EOS 450D camera, when used in the Auto mode ..all is well when I try to use it in P,Tv,M or A-Dep mode the shutter does not complete its function but stays open until I press the shutter button again. Any clues? kp

Try removing the lens with the camera off and re-mounting it. Before doing so, check to make sure the contacts on the lens and camera body are clean and not damaged. If that doesn't help try gently pressing on the front of the lens (not the glass) while pushing the shutter release button half way down and if it works then you've got a poor fit between the lens and camera body.

Spillage or impact damage that breaks lands in the flexible top cover circuit can cause this problem, as can sand which wears away traces on the switch contacts on the circuit itself. Impact can also cause the flex from the top cover topull loose or twist sidewase in the flex connector on the main circuit. In most of the Canon Rebels the top covers are only available as complete assemblies.

Your camera is broken, dial and circuit board underneath needs replacement.

Hi, It sounds like the 'mirror up' option is selected since the mirror will stay up for 30 seconds then close and it wouldn't be active on any of the basic settings. You'll want to go into your settings menu and disable mirror lockup. If you need anymore help just let me know =)

There are several contributing factors to this problem and I'll try to list a few that may be the cause.
All Canon EOS camera auto focus modes us contrast to focus this means simply that no contrast there is no focus. There is a small green dot in the lower right corner of the viewfinder that will come on and stay on solid when auto focus as been achieved. By default the shutter will not operate "click" if auto focus has not been made.

Here are a few examples of where auto focus will ether search (focus back and forth) or fail completely.

A solid painted wall, glass between the camera and subject, mirror, chrome, any large body of water, clear sky. Another place you wouldn't expect is clear skin in your subjects face or body.

Cameras with multiple focus points and set to other then the middle will have a problem if the photographer is still attempting to use the center focus point.

Look for the green dot in the lower right corner of the viewfinder that's your focus confirmation.

if you cant see anything on screen and you get busy massage on view finder then main pcb fault you need to replace it

this may have to do with the lens rather than the camera, try swapping the lens with another one and see if the same problem happens in AF mode with the new, borrowed lens, also remove lens and check that the gold connector between the two are clean carefully wipe with a dry q tip but be careful not to allow dirt to fall into camera body.

The ISO is set to Auto and can't be changed when shooting in Basic Modes (all of the icons and the green circle). ISO can only be adjusted in Creative Modes (P, Av, Tv, A-DEP, M). If you want to adjust the ISO in Creative Mode, press the ISO button and then turn the dial next to the shutter trigger.

Check whether there is anything obstructing the range sensor just above the rear LCD. The sensor could be thinking that your face is near, thus turning off the display. Also, you should be able to use the Disp button even in auto display mode, which might make the display not show anything by default.

No. You can only use the camera in manual mode, setting the shutter speed to, say, 1/125 sec and the aperture: according to the working aperture on the flash. The flash has to be in auto mode. The physical connection between the camera and flash can be either a standard PC cord, originally supplied with the flash plus a hotshoe-to-PC-female "cube", or an SCA305a cable plus an SCA301 standard foot. Of Metz 45 series only the 45CL4 Digital together with an SCA3102 M4 module is dedicated to the Canon EOS digital series.