What are the parts of the 20D inside, when looking at without a lense?

[EricKonieczny]

Now that I have cleaned my 20D sensor a few times. I am wondering what the other parts inside are?

The first thing you see is the mirror/ peice of glass that flips up for senor cleaning?

Behind that is another mirror it looks like that also flip up simultaneously.

But what is on the top of inside compartment? It is hazy white with the AF focusing points?

Is it safe to clean all these peices?

I am just guessing at these parts, please correct me if I am wrong.

I guess my problem is, when I clean the sensor and these other parts are dirty, and i then snap a few pictures, and the dust then gets on the sensor again.

How the heck do you clean the rest of the inside?

[Andy_T]

Eric,

if you don't know what these pieces are, you should *really* not be cleaning them :lol:

No kidding, most likely you're talking about the focus screen. The mirror is very sensitive (much more so than the sensor!) and forcing it out of alignment might screw up autofocus.

Best regards,
Andy

[Tom W]

Don't touch the mirror - The reflective surface on the mirror is very delicate, as it is much more precise than that of ordinary mirrors. The hazy-white screen above the mirror is the focusing screen. It is part of the scheme that gives you the ability to see your images clearly in the viewfinder. It works almost like a back-lit projection TV. If you mar the finish of the focus screen, it won't affect your pictures but it will harm the images that you see through the viewfinder.

Its best to just blow dust off these parts, and not to touch them. Especially the mirror since its very delicate and is part of the autofocus system.

[EricKonieczny]

Eric,

if you don't know what these pieces are, you should *really* not be cleaning them :lol:


Thats why I am asking. I have only cleaned the sensor. I have to learn some how and aksing questions on here seems like a good place to learn.

Thanks

[lancea]

... I guess my problem is, when I clean the sensor and these other parts are dirty, and i then snap a few pictures, and the dust then gets on the sensor again...
Interesting replies about the mirror and autofocus, so thanks for posting this question. But if you really have so much dust and it's a problem after just a few shots, and a blower brush doesn't do the trick, then I think you'll have to get it professionaly cleaned. So far I've only found dust to be noticable on the sky, and that is easily retouched. I've avoided taking those test shots that show up the dust because they make things appear much worse than they are.

[EricKonieczny]

So where do I send it to get cleaned? To Canon directly? :mad:


Who has done this? Cost, time frame?


Can anyone tell me what the exactly do? Do they take the camera apart or just do a better job than I can do , without experience?

[Rob612]

Eric,

if you don't know what these pieces are, you should *really* not be cleaning them :lol:

No kidding, most likely you're talking about the focus screen. The mirror is very sensitive (much more so than the sensor!) and forcing it out of alignment might screw up autofocus.

Best regards,
Andy

Ditto on that ! And let me add something.

Remember that the mirror, as in all SLRs is made of extrathin glass and with the reflective coat on the upper side (i.e. if you clean it, you'll clean the actual mirror coat, if damaged, you' are on your way to a repair shop). VERY delicate.

The fresnel lens (or if you refer the focusing screen is almost as delicate as the mirror). Plus, its where the AF sensor are, any damage to those little guys and you've got a problem.

In other words blow gently everything, but do not attempt anything else if you do not REALLY know what to do.

Hope this helps

[Tom W]

Ditto on that ! And let me add something.

Remember that the mirror, as in all SLRs is made of extrathin glass and with the reflective coat on the upper side (i.e. if you clean it, you'll clean the actual mirror coat, if damaged, you' are on your way to a repair shop). VERY delicate.

The fresnel lens (or if you refer the focusing screen is almost as delicate as the mirror). Plus, its where the AF sensor are, any damage to those little guys and you've got a problem.

In other words blow gently everything, but do not attempt anything else if you do not REALLY know what to do.

Hope this helps

That is all true except that the actual autofocus sensors are not up on top, but are down at the bottom of the mirror box. Light is directed to them through the secondary mirror. The primary mirror that you see has unique reflective capabilities where a small portion of the light passes through to the secondary mirror where it is reflected to the autofocus sensors.

This little image from Luminous Landscape should illustrate things a little:

http://www.luminous-landscape.com/images7/opticpathbig.jpg

Basically, the yellow line is what you see in the viewfinder, while the green line is the path that the autofocus system uses. Which means that the reflective coating on the mirror is even more delicate than most would think since it has a precice amount of reflectivity.

[Rob612]

Never too late to learn something new. Thanks.

[Tom W]

Never too late to learn something new. Thanks.

That's OK. I do remember reading somewhere that some older SLR cameras had the AF system up in the top rather than below, so this may depend on the manufacturer or type of camera.