What role does the mirror play...

[paulhillion]

in the viewing/capturing of an image?

My reason for asking is the age old problem of dust on the mirror. However I've read all the 'cleaning' threads & as it doesn't seem to effect the final image I've not bothered (nor intend to) to clean or indeed use a cleaning cloth on it. I have however given it a quick going over with a blower which doesn't seem to dislodge the slight amount I can see. There are a couple of small spots visable through the view finder but again I'm not to worried about it.

Thanks.

[DocFrankenstein]

Mirror by itself, (if the cam is focused properly) will have zero effest on the final image. It flips up and out of the way the light hits the sensor.

[Penguin_101_1]

If I remember right (it is Midnight) the mirror allows you to see the image through the viewfinder giving you the advantage that you can see exactly what the image will look like unlike other cameras.

[Jesper]

Here is a page that explains how SLR cameras work and what the mirror is for:

http://entertainment.howstuffworks.com/camera7.htm

In short: The mirror is only necessary to enable you to look through the lens (through the viewfinder) before you take the picture. When you press the shutter button, the mirror flips up and lets the light pass from the lens to the film or sensor. So the mirror doesn't affect the final photo.

[arumdevil]

I may be wrong about this but does not the mirror also feed the AF CCD? if so then any dust on it could fool the AF system to thinking the image is in focus ????

[forrest64]

The mirror, I believe, also contains the exposure sensor

[jyrgen]

I believe mirror lets through some light, which in turn is directed to autofocus and metering sensors via some additional little mirrors.

[forrest64]

When I look at the mirror on my 10D I see thin gold colored patterned foil. I have to guess these are, at least, the exposure sensors and perhaps the AF sensors.

[AzzKicker]

ALl the mirror does is bounce what comes in through the lens to the view finder. Thats its only purpose.


You can have a block blob on it and take a pic and the pic will be fine. YOU HOWERVER wont see what your taking a pic of through the viewfinder though lol

[arumdevil]

ALl the mirror does is bounce what comes in through the lens to the view finder. Thats its only purpose.


You can have a block blob on it and take a pic and the pic will be fine. YOU HOWERVER wont see what your taking a pic of through the viewfinder though lol

That can't be true. somewhere in there is a little CCD for the Auto Focus (and some kind of exposure sensor). I don't know exactly where it is but logically it would have to be the same distance from the lens as the film/imaging CCD is. i certainly can't see it anywhere between the mirror and the back of the lens in any case.

so following this logic it is either behind the mirror (and the mirror does seem to be semi transparent) or up near the viewfinder somewhere.


somebody on here must know the answer!!

[Tom W]

This might help:

http://www.luminous-landscape.com/tutorials/understanding-series/viewfinders.shtml

[Matti J]

I believe mirror lets through some light, which in turn is directed to autofocus and metering sensors via some additional little mirrors.

Yes. The little mirror directs the light down to the base of the mirror box, where the phase detection sensors for AF and exposure metering sensors are located.

Matti J.

[AzzKicker]

I stand corrected

[jyrgen]

Found another nice picture (http://www.dpreview.com/reviews/canoneos10d/images/10d-specs.jpg) of 10D.