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05-19-2011, 10:22 AM   #1
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Dust on Sensor

The dust Alert shows a lot of dust on the sensor.
What impact on the pictures ?
Is it Stains.
Thanks

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05-19-2011, 10:38 AM   #2
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That looks like a lot of dust, but Dust Alert can be tricky.

I would first repeat the test making sure you are imaging a clear field - I find a blank white sheet of paper held fairly close to the lens works well, but be sure there are no marks, creases, or shadows on the paper as that will through the Dust Alert off (it keys on contrast) and can produce images like the one above.

If you get the same result, I'd try a normal exposure of a blue sky (f16, iso 100, infinity focus) to confirm, before getting out the blower, swab, etc.
05-19-2011, 10:55 AM   #3
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That can't be dust. If you used a piece of white paper, any crease or shadow will give this kind of effect.
The better method to check the dust is the following. On a day with very clear sky, set the camera in manual focus, focus at infinity and take a pic of the sky at a 50mm or more, ISO 100, using an aperture of f20 or f22. Any bit of dust will show up in that pic.

Last edited by causey; 05-21-2011 at 08:17 AM.
05-19-2011, 01:44 PM   #4
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Shoot a blank (totally blank) wall or sheet of paper. And it must fill the frame. Otherwise you'll get false positives.

The dust alert is a nice feature, but it's tricky to use correctly.

05-19-2011, 05:18 PM   #5
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Seems like there's been a few posts like this lately. The dust alert function is useless. Here's how you test to see if you have dust on your sensor

1) Put camera in Av mode
2) select the highest possible f number, probably f22
3) change ISO to 100 or 200 (no auto iso)
4) switch the camera from AF to MF
5) manually spin the focus ring of your lens to infinity
6) find a plain white wall or door
7) take a picture of it from about 2 feet away, don't worry about the long exposuretime. A bit of camera shake is fine too, in fact I deliberately move it around a bit. Make sure that while wall fills the frame though, dont include objects int the pic.
8) import the picture you just took into your photo editor
9) flip the picture vertically
10) apply auto-levels adjustment to the picture

Now you know exactly whether you have dust and where those dust specks are. If you have a spot in the top right of the pic, then that dust will be in the top right of your sensor as you face the sensor (as you've flipped the image vertically remember, otherwise the dust will be in the bottom right corner).
05-20-2011, 04:33 PM   #6
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QuoteOriginally posted by gerardbaron Quote
The dust Alert shows a lot of dust on the sensor.
What impact on the pictures ?
Is it Stains.
Dont panic, those tiny dust particle gets in when you keep changing your lenses frequently. My K-r showed more than that few days back.
It can be simply removed with Sensor shake. Run it once or twice, all the dust will be removed from the sensor.
There is an option that even allows you to shake the sensor at startup (my k-r has that). I dont use it (why to shake sensor unnecessarily )
05-20-2011, 08:21 PM   #7
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Actually, the dust sensor works if you use it correctly. I agree though that it's probably easier to check the old fashioned way.
05-20-2011, 08:53 PM   #8
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The dust sensor works very well. I have found opening a new blank MS Word document (or anything to show a white screen) and making it fill the monitor makes an excellent target. The resulting dust pic also shows the mount for orientation.

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