40D - Small debris on focusing screen

Well, I figured it out. I had to pull the tab towards me (when facing the front of the camera, ie pull it towards where the lens would be), not press it down. This whole time I thought "applying gentle pressure on it" meant to press it down. A slight pull opened it up. Should have thought of it earlier...

Thank you, qtaran. That guide will be helpful for when I actually change the focus screen.

I wonder how that chunk of dirt got in there in the first place?

fiveFPS wrote in post #3927285
I wonder how that chunk of dirt got in there in the first place?

They are not sealed airtight. They also sometime ship with debris. Because of this,this website recommends cleaning the mirror box before cleaning sensor.

Keep in mind that the focusing screen, often referred to as 'ground glass', is NOT glass. Do not scrub it. Once dirt gets embedded in it you will not get it out and it will need replaced. I know from experience.

Reefbone wrote in post #3928960
Keep in mind that the focusing screen, often referred to as 'ground glass', is NOT glass. Do not scrub it. Once dirt gets embedded in it you will not get it out and it will need replaced. I know from experience.

I second that Reefbone. When I first got my 400D I tried swabbing it ('cos I am a fool) and it ended up scratched to buggery. When I replaced the screen I realised why; the screen is made of very delicate plastic.

I was really p*ssed off because I used an optical swab from work which I use all day to clean laser mirrors and I thought these would be safe.

The first rule of the focus screen is that you do not touch the focus screen.

The second rule of the focus screen is that you do NOT touch the focus screen.

my 40D also came with a big chunk in the viewfinder (on the prism or screen) and it's currently at Canon being cleaned. It also had what looked like an ink smear on the inside of the top LCD. Both are simply cosmetic and don't affect function, but for a brand new camera to come out of the box in this condition at this price is hardly acceptable in my book. When I do (and I will) get some junk in my viewfinder I'd like it to be because I've gotten a whole lot of use out of the camera.. at that point I'm happy to consider it "building character"

I too should add that I tried to clean my own focus screen and made the problem much worse. I will be paying canon to replace it if they don't do it as a courtesy.. but of course it shouldn't have been necessary to attempt to replace/clean it right out of the box in the first place. I've had good experiences with Canon service and the 40D seemed awesome in every other respect, so I'm sure I'll be pleased when it returns.

Menocu wrote in post #3929292
my 40D also came with a big chunk in the viewfinder (on the prism or screen) and it's currently at Canon being cleaned.

I am glad I did not have to have mine serviced for such a minor thing. But I agree with you that it is hardly acceptable of a brand new camera. My first thought when I saw that debris in the viewfinder, "Are you kidding me!". I guess it can't be helped though. Some units are just bound to have some type of "defect" fresh out of the factory.

Hello - I just had a bad experience doing this and thought I'd pass on some tips.

Fibers on my focus screen prompted me to remove and clean, so I searched the web and found this and other forums.

Yes - removing the screen is easy once you know how - but the first time you do it, you will probably screw it up. Not having purchased a new screen, I didn't have the proper tool that everyone talks about - so when I pulled on the clip (with very little force), the thing opened immediately and dropped. The focus screen bounced and was knocked into an awkward angle. Grabbing the screen by the tab with one set of tiny tweasers wasn't working, and so I gently grabbed the entire thing to pull it out. Mistake two: I should have used something rubbery - cause I wound up scratching it. dang!

So advice # 1 - don't let it drop. use a finger or something to catch it coming down. Advice #2 - do not touch the screen by anything but the tab and sides.

I cleaned it and put it back .. and it was more dirty than before!!! I repeated this process about 8 times before I managed to get it clean with no specks. On one occasion, I pulled the screen out - not clearing the cradle enough, and scratch it again!! It barely touched as it was coming out. It seriously scratches WAY too easily.

Visually, it is difficult to see these scratches through the view finder. But what is noticeable is the image now has halos. Which sucks. This may affect metering.

In my case, those fibers that originally bugged me were actually on the bottom side of the screen. I should have used an air blower or lightly brushed them off, from the inside of the cam rather than removing the screen.

I think it is nonsense others reporting that this is easy to do in the field. This thing is so delicate it is unbelievable. i can't even imagine carrying a spare without damaging it. And it is also an incredible dust magnet. i wouldn't do it again without a damn good reason.

If you do chose to remove yours, be very very careful. try to work in a dust free environment and have non metallic tools to work with... and be prepared to spend $35 to replace it too. I also second the advice not to rub it with a cloth.