mirror & Q-tips need help

Hi to all
i'm new , and i'm new user of a canon 350D

after bought it , i found some dust inside the focusing screen

i opened the camera and with a "dry" Q-tips( it did not leave dust) i did clean the mirror , the up side of the mirror.
i did not make strong pressure , i touched it really softly

could i damage the camera?
are there sensors on the up side of the mirror (what i can see after i dismantle the lens)?

if i did damage the camera , how can i unsterstand it ? i'm really a novice , a dummy

thanks
kinds regards & have a nice day

Do Not...I repeat...Do NOT do anything to the mirror more than use a rocket blower on it. The coatings on the mirror are very delicate and meant to be semi-transparent. Stick the Q-tip in your ear and keep it out of the mirror box.

Woolburr wrote in post #2275680
Do Not...I repeat...Do NOT do anything to the mirror more than use a rocket blower on it. The coatings on the mirror are very delicate and meant to be semi-transparent. Stick the Q-tip in your ear and keep it out of the mirror box.

agree here... use a rocket blower only... if you are having trouble getting things clean then send them in to Canon or take them to a store...

sari

Woolburr wrote in post #2275680
Do Not...I repeat...Do NOT do anything to the mirror more than use a rocket blower on it. The coatings on the mirror are very delicate and meant to be semi-transparent. Stick the Q-tip in your ear and keep it out of the mirror box.

thanks i know and i will not use it again

i know i should not use a Q-tip on the mirror!
but my question is :

1) did i damage the mirror?

2) how can i see if there is a badly operation of the camera?

I have a spec on the screen above the mirror in both my 300x and my new 400d a rocket air won't shift it and other than bugging me when framing, it doesn't effect my images. can I use a Q-tip on this or is it a pro clean job?

If you look at the mirror and don't see traces of the Q-Tip, you didn't do significant damage to it. But don't do it again. If the focus (on all points) is still working properly and all 3 metering modes used on a plain surface give consistent results, you probably didn't affect it this time. Actually, damaging the mirror will affect your viewing and metering more than focussing, since damage to the reflective surface will prevent light from reaching the focussing screen and metering cells, while the focussing sensor is fed by light passing through the front mirror.

If a speck's on your focussing screen, don't use a Q-Tip - they'll leave lint behind and you're likely to be worse off than before. The screen's very fragile, so if a Rocket Blower won't shift it, learn to live with it. If you take it into a shop they may just wipe it with a brush or cloth and mar the matte surface.

thanks JON

what can i use for a plain surface?


sorry for my poor english

Bare wall with even lighting; concrete floor, again with even lighting; grassy field, to name a few.

Jon wrote in post #2276011
Bare wall with even lighting; concrete floor, again with even lighting; grassy field, to name a few.

thanks JON

here is 17 (5pm)
almost evening
in my room , lamp light on , the camera can't focus on my white room wall

this means that i should change the mirror?

You need something for the camera to focus on to test that. The plain wall is just for metering. You may need to go to manual focus while checking the metering.

A front surface mirror is very fragile, but touching it very lightly with a q-tip is not going to wreck the mirror. The mirror itself is actually a bit more durable than many are making out as anyone who has owned a reflective telescope for any length of time can tell you. The damage is more likely to occur in that any pressure applied against the mirror will knock it out of alignment before it will remove the coating. If the dust is annoying, use the rocket blower so something similar, not canned gas. That usually knocks it off. If it’s still there, then try to live with it. It won affect you image quality. If it bugs you so much that you just have to get rid of it, don’t use a dry q-tip, use a micro-fiber cloth and use the lightest of touches you possible can just on the speck itself. Or, take it to a camera shop and let the gorilla behind the counter do it for you.

Jon wrote in post #2276177
You need something for the camera to focus on to test that. The plain wall is just for metering. You may need to go to manual focus while checking the metering.

ok i did ,and the camera did focus well with every focusing points,and i did shot many pics

for the metering what should i look in the pics? to detect if it did a correct metering(i'm a novice )

gjl711 wrote in post #2276391
A front surface mirror is very fragile, but touching it very lightly with a q-tip is not going to wreck the mirror. The mirror itself is actually a bit more durable than many are making out as anyone who has owned a reflective telescope for any length of time can tell you. The damage is more likely to occur in that any pressure applied against the mirror will knock it out of alignment before it will remove the coating. If the dust is annoying, use the rocket blower so something similar, not canned gas. That usually knocks it off. If it’s still there, then try to live with it. It won affect you image quality. If it bugs you so much that you just have to get rid of it, don’t use a dry q-tip, use a micro-fiber cloth and use the lightest of touches you possible can just on the speck itself. Or, take it to a camera shop and let the gorilla behind the counter do it for you.

ok thanks for you kindness

Do all 3 settings give you comparable exposure? That's why a uniform surface - to rule out differences in the different metering areas.

Jon wrote in post #2277218
Do all 3 settings give you comparable exposure? That's why a uniform surface - to rule out differences in the different metering areas.

look
1) http://img206.imagesha​ck.us/img206/823/img00​01qc2.jpg

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Hmm, The center image is a little darker.

Image 1 - 1/3 @f4 ISO100 Metering - Pattern
Image 2 - 1/4 @f4 ISO100 Metering - Partial
Image 3 - 1/3 @f4 ISO100 Metering - Average

Not a big differance, but I'd keep an eye on it and try a few other scenes.

On a quick test with my 5D, I got the same readings on my wall (1/60 @f2.8 ISO3200) regardless of what metering mode I was in.

-Johnny