I recently aquired a used Canon 450D, which the previous owner said was broken. I'm new to photography and SLRs so please excuse some of the ignorance following.

After digging a bit around the last couple days, and trying to understand how the camera is working I found the following is missing:

  • Focusing screen
  • Focusing screen spring/holder
  • Probably shims/washers for the focusing screen (I understand the thickness here has to be calibrated for MF).

Of course this leads to problems with using manual focus. I can still partially see through the viewfinder, but I have to use live view to manually focus. The camera also takes in too much light, so I assume the missing focusing screen affects the metering also. In live view the exposure seems good.

What puzzles me is that the autofocus is not working at all. It searches for focus, but seldom manages to lock (usually only in servo mode), and it is never in focus. Using live view it is able to AF, but very slow. From what I gather, the focusing screen should not affect the AF as the light for the AF sensor never passes this screen. I guess it can be affected by the metering, but the problem persists in very bright outdoor to indoor conditions.

Could something be broken with the AF sensor, or the mirror reflecting the light down to the AF sensor? I have not tried other lenses, but I can borrow from a friend if that makes sense.

Any tips on what might be broken, and how to check and fix it is much appreciated! I was hoping to troubleshoot this on my own, due to my student economy and lack of service centers nearby.


Edit: It appears the submirror is completely missing! No wonder the AF did not work...

Rephrased question: is this something that can be fixed ?

  • 1
    \$\begingroup\$ It sounds to me like someone has had it apart to try to fix it and made it worse! \$\endgroup\$ Aug 28, 2013 at 8:20
  • \$\begingroup\$ According to the previous owner (who I trust), this should not have been the case. The damage should have happened in extremely cold weather (-25 C). I also found the likely reason for AF not working: the submirror is missing! \$\endgroup\$
    – rhkarls
    Aug 28, 2013 at 8:48
  • \$\begingroup\$ oooh well that's certainly not going to help!!!! I couldnt call that "likely" i'd call that definitive. I'm not sure of the construction of the 450D, but my Nikon's have the metering CCD down there too... \$\endgroup\$ Aug 28, 2013 at 8:50
  • \$\begingroup\$ Canon exposure meter sensors are in the pentaprism/pentamirror housing. \$\endgroup\$
    – Michael C
    Aug 29, 2013 at 13:55
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    \$\begingroup\$ My fear would be that if this is what's been done to it, what else has been broken/botched that you haven't discovered yet? \$\endgroup\$ Oct 27, 2013 at 20:20

1 Answer 1


Anything can be fixed with enough resources. The question in this case is if it would be worth the resources needed to fix your 450D? The answer is probably not. If you could pick up another 450D that has other broken parts but has the ones you need intact and could do the work yourself perhaps it would be, but replacing the submirror is a lot more intricate than replacing the viewscreen.


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