question on the 20D and the mirror mechanism...

[edp]

is it relatively ok to lift up gently on the mirror to dust out behind it with air (bulb or canned)? I used to be able to do this with my old film cameras to clear out whatnot around the light meter areas, but not sure on the dslrs. it's tight, but seems like it's just a spring loaded return, not a rigid mechanism. Any exploded diagrams?

[tim]

DON'T DO IT.

There's an option in a menu to lock the mirror up so you can clean it. On the 300D it's something like "clean sensor", the 20D will be similar.

[Huckaback Photo]

Best advice is leave well alone... this should apply to any camera with mirror in.
the mirrors used are unlike a mirror in the house, where the silvering or refflective surface is behind the glass. when cleaning a refflex mirror inside a camera body you are cleaning the actual refflective surface, get finger prints or scratch marks on this dellicate surface,then a bit over enthusiastic rubbing to remove same and you have a nicely damaged mirror, in need of replacement possibly !!
some cameras have mirror lock, this can be usefull at times. its really up to you but that is my advice.
Martin

[Ikinaa]

page 36 in the 20D-manual : Cleaning the CMOS sensor
describes how to lock up the mirror

[edp]

but that's not what I was really discussing. what's the paricular operation of the mirror mechanism. I was wondering about the actual mechanics, either in an illustrated diagram or any other info.

[Huckaback Photo]

Tim you just got in while i was typing my answer to above .
DON'T DO IT. is def the right answer..
Now if you decide to clean the sensor even more care is required (something else to damage )
Mirror lock does not open the shutter so sensor is not exposed.some people use mirror lock as a way of preventing extra vibration if you like ( ie. put a bellows on a tripod mounted camera with high magnifications etc)
so once focus is achieved you dont really need the mirror again so all that moves is then actual shutter curtain.
with bulb setting used the sensor is once again open of course.
take lens off body look just below bottom edge of mirror you will see shutter curtain /cover closed
i guess this is what needs cleaning. ??

Yes the mirror will deffinately move if you lift it, my point really is why risk any damage , use mirror lock if available sensor is then closed and mirror is out of the way
hope this helps.
Martin

[edp]

while I puffed away some dust there, I got curious as to the actual operation of the mirror and it way it is lifted/released. I suppose it is a spring return and not fully driven in both directions (esp during continuous mode), and was wondering if there was more info on it.

[Huckaback Photo]

Of interest to others
With 1D mk 2 Mirror lock is set with custom function . C.Fn-12, once set it reverts after 30 secs.
during that 30 secs you press shutter again to take shot .
Check your 20 D manual as recomended by Ikinaa above.
Martin

[RichieHatch]

Is this diagram any use to you:

http://www.dpreview.com/reviews/CanonEOS20D/Images/specsview.jpg

Richie

[Monito]

Don't used canned air. It is much too powerful. It will push dust and lint deeper.

Don't try to use the mirror lockup if the 30 second rule might bite you. As others have said, there is a specific sensor cleaning function that locks the mirror up and opens the shutter.

Don't use fluids on the sensor if you can at all help it. Even regular brushes are too harsh and can scratch it. There are special brushes that can be used.