50D mystery dust location?

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vaizki

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Jukka
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So I picked up a cheap 50D for a backup camera (my 40D is still in pieces waiting for a new shutter install by yours truly). It has a pretty awful collection of dust spots and even little hairs visible in the viewfinder.

They're not on the eyepiece outside or the mirror. Blower treatment - no change at all. They're not on the focusing screen - they are visible even when I remote the screen (and I did blow-clean it also while I had it out). They don't seem to be on the bottom of the pentaprism either (thankfully).

So where is this dust.. between the eyepiece and the pentaprism? And how do I get it out.. As the pentaprism is a solid chunk of glass, I can't think of other places.
 
If they're visible when using live view then they aren't on the pentaprism, its either lens or mirror really, theres nothing else left as if on the sensor they wouldn't show through the viewfinder, if however you cant see them when looking through the viewfinder then they will be on the sensor and you need to get some cleaning swabs.
 
Probably between the focusing screen and the pentaprism. Sounds like someone may have had a different focusing screen in it at some time.
 
Ok so just to be clear.. it's visible on the viewfinder but not the pictures. It doesn't seem to be on the mirror as a) some of it is in perfect focus and b) I can't see anything on the mirror under bright torch light. And I removed the focusing screen while checking.. and can't see anything up there either but of course it might be there. Just had another rocket blower clean on the pentaprism underside / focus point overlay where the focusing screen normally rests.. no difference :(

I'm pretty convinced now that it's between the eyepiece and pentaprism.. but would it be in focus if there? Some of the spots are out of focus though..
 
Probably on the inside of the focus screen, and possibly blown there by a rocket blower.
 
I reckon, like is the case with all the Canon cameras with changeable focus screens, the dust is actually behind the focus points screen. This is different to the focus screen and can be seen once the focus screen is removed.

I'm sure these can be removed and a rocket blower can be used to get the crud out, but I wouldn't be able to tell you how!

My 5D has the same problem, but just a few specks of dust fortunately :)
 
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