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04-02-2011, 08:46 AM   #1
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odd issue with focusing

Oy lads!

Recently I had to clean up my K 10 coz I had some markings on the pics. The problem was that the dust was not on the mirror or sensor but on the plastic thingie above the mirror. It a rectangular piece of translucent plastic with some indented marks where it can be seen the focus points. Well after I cleaned the dust I put it back and I did some tests. It appears that autofocus does not work properly. I said it appears because the image is not clear only trough the eyepiece. It's 100% sharp on computer. So actually what seems to be blur trough the eyepiece is sharp in reality. Also the lens is working fine on manual focus. Pictures are sharp on computer and trough the eyepiece. My conclusion is that is nothing wrong with the lens or autofocus but with that plastic piece which I probably mounted back wrong. Funny is that I still have "dust" on my pics.

I need to mention that now I'm faraway of any kind Pentax store so I need to solve this problem by my own. Any sugestions?

Thanks a lot,

04-02-2011, 08:55 AM   #2
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You have 2 separate and distinct issues.
1) You do have dust on the sensor. You may not be able to see it without a loupe but it's there. The dust doesn't have to be big. Remember that the sensor has 10.5 million pixels in a small area. So the dust can be nearly microscopic to cover a dozen pixels or so.

2) You've taken out the focus screen. It's a fragile part and easily scratched. Most likely you put it in crooked or upside down. Just take it out carefully and flip it over. Make sure the metal frame is closed properly to lock it in place. It's annoying but unless it really hinders your ability to take shots, I wouldn't clean it more than using a rocket blower.
04-02-2011, 09:15 AM   #3
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Only dust on the sensor will show on the images. Dust elsewhere (mirror, focusing screen) has no impact on the image.
04-02-2011, 09:17 AM   #4
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Man're quick. So I have dust on the sensor.

In the meanwhile I've checked a service manual for Pentax and learned a new word: focus screen . I also checked the position of this screen and it looks right. Just like in the picture from the manual. Also it is said there something about adjusting the focus screen, lens and parallax effect. It's sounds complex but I'm still reading.

Many thanks Peter Zack

04-02-2011, 09:27 AM   #5
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Another thing that might go wrong would be forgetting the shim or putting that on the wrong side of the screen.
04-02-2011, 01:27 PM   #6
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Jolepp the shim is in right side toward the lens. Also the focus screen is staying with the flat side downward and curved side upward. This is how is looking in the service manual also. See attachment. The metal support that holds the focus screen does not allowed the screen to slip to right or left. So everything look alright. And still the image is blur trough the viewfinder.
Attached Images
04-02-2011, 04:50 PM   #7
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Did you perhaps bump the diopter adjustment on the viewfinder eyepiece somehow?
04-03-2011, 12:22 PM   #8
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QuoteOriginally posted by bimjo Quote
Did you perhaps bump the diopter adjustment on the viewfinder eyepiece somehow?
nah...the diopter is fine. I'm afraid I'm gonna swish to manual focus until I'll rich a Pentax dealer.

Thanks for support lads!


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