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08-13-2008, 09:17 AM   #1
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dust-- mirror or sensor?

I am seeing specks of dust through the viewfinder, and with each lens change (i.e., it's not the lens) . The small brush blower does not seem to work. I am asssuming that, since I can "see" it so easily, it's on the mirror, which is much safer to clean than the sensor, which is always set to"sart up action"

Is my "assumption" or logic simply wishful thinking, and thus I may need to clean the sensor?

If it's not the sensor, how "aggessive" can I be with the mirror? Can I use a "lenspen"? Damp lens cleaner paper? A more powerful blower? Or simply a more powerful blower?

08-13-2008, 09:22 AM   #2
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neither. It's most likely on the ground glass -- the focusing screen you look at when peering thru the diopter.

see here:

https://www.pentaxforums.com/forums/pentax-photography-knowledge-base/10326-h...een-k100d.html
08-13-2008, 09:34 AM   #3
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Hmm.. Would the dust then show up on the photo?

I am very hesitant to change anything "inside" the camera (bad history with things far less delicate than the K10d!)

Can a get a photo store do it for reasonable cost?
08-13-2008, 09:57 AM   #4
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QuoteOriginally posted by tmacdon Quote
Hmm.. Would the dust then show up on the photo?

I am very hesitant to change anything "inside" the camera (bad history with things far less delicate than the K10d!)

Can a get a photo store do it for reasonable cost?
No, dust on the focus screen will not effect any pictures you take.

If you want to see the dust on your sensor, get a lens with the smallest aperture possible -- say f/32. Point at well lit white wall and take a picture.

The small aperture will bring any dirt on the sensor into focus. You'll see the dirt quite clearly on the taken photograph.

Yes, if you don't feel comfortable mucking with stuff inside your camera, have a professional do it.

Here's a nifty animation and associated text to better visulaize what these parts do in your camera.




The mirror in a single lens reflex (SLR) camera reflects light upwards through a pentaprism to be viewed. The pentaprism turns the image the right way round for the eye to see. When a picture is taken the mirror flips up to allow light to hit the film at the back of the camera. As the eye sees the image through the main lens it appears identical to that produced on the film.

08-13-2008, 11:02 AM   #5
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Nice description there. If you are seeing dust on the ground glass don't worry. Unless its really annoying you. The ground glass is made of a very delicate rough material, if you get grease on it you are screwed, even water can be a problem. Thats no joke. I had a couple of specks on my MX a few months ago and actually tried to clean it with a lens cloth, leaving huge dark smudges everywhere. Unuseable.

I think the best option is: "A more powerful blower? Or simply a more powerful blower?"
Dont push the nose inside the camera though, outside the mount only.

I agree that getting a professional on it is better. Just removes the worry!

p.s. I also have dust on my ground glass at the moment. I'm not worrying about it at all.
08-13-2008, 01:11 PM   #6
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That dude's staring at her butt...

c[_]
08-13-2008, 01:29 PM   #7
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Yeah, probably not the mirror. The mess --hair and dust-- are very noticable on the images AND in the view finder. My assumption is that if it was the sensor, I would not see any dust till it was processed. Am I wrong?
08-13-2008, 01:45 PM   #8
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QuoteOriginally posted by tmacdon Quote
Yeah, probably not the mirror. The mess --hair and dust-- are very noticable on the images AND in the view finder. My assumption is that if it was the sensor, I would not see any dust till it was processed. Am I wrong?
You won't see sensor dust in the viewfinder. You'll only see it on the photo. Sounds like you have dust on the viewfinder screen and the sensor.

Rocketblower time for you!

08-13-2008, 01:58 PM   #9
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If the dust looks shape through the vf, it is on the upper side of the screen. If it looks oof, it's either on the lower size of the screen or prism.
08-14-2008, 09:51 AM   #10
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Thanks folks,

I took the K10 to professional repair shop. There was dust on BOTH the sensor and the focusing screen, which they got out for a for a reasonable rate ($ 60). They basicaly said that all precautions and devices in camera "help" but dust is inevitable. So, it would appear, are periodic professional cleaning.
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