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09-18-2008, 01:30 AM   #1
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Dust on sensor or lens?

Hi,

In the situation where I have only one lens and I need to find out if dust spots are from dust on the sensor or the lens can I just put the white camera body cover and take a shot while pointing the camera to a light source? I got a totally clean white image as a result but I am wondering if a lens is needed in front of the sensor (due to the path incoming light rays take etc) to make dust spots visible.

Thx

Nirudha

09-18-2008, 01:39 AM   #2
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Dust on the pictures from a lens would have to be huge to show up. Probably 3-4 mm at least. The most likely cause of spots on your picures is dust on the sensor.

You can take a shot of a white wall with the lens off and nothing covering the front opening of the camera if you want to (but you will add more dust most likely). The best way is with the lens on and in manual focus, take a shot of a cloudless bright sky. Then in any software, boost the contrast way up. Dust will show up very clearly.
09-18-2008, 02:29 AM   #3
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Use a stopped down aperture, F16 or so. It shows dust up much better.
If you have a K20D, use the dust aleryt feature.
I second Peter's response, MOST probably sensor dust, very common, happens alot, be careful on removal.
09-18-2008, 04:27 AM   #4
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Thanks

QuoteOriginally posted by Peter Zack Quote
You can take a shot of a white wall with the lens off and nothing covering the front opening of the camera if you want to (but you will add more dust most likely). The best way is with the lens on and in manual focus, take a shot of a cloudless bright sky. Then in any software, boost the contrast way up. Dust will show up very clearly.
I did find quite a bit of dust particles by taking a sky shot. Now to use a blower and clean. I guess it gets trickier if that doesn't do the job.

You mentioned that a naked DSRL would work (and let dust in during this time.) Does that mean having the lens cap on would not work? Is the light too defuse then?

09-18-2008, 06:03 AM   #5
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If you use the white body cap i suppose that would be basically the same and work fine. But the lens and sky shot (stopped down as Marlon mentioned) will work best. I've never done a wet cleaning on my sensors (never had to) Just a good Rocket Blower and everything was fine. Just take the sky shot. see what's there and then clean the sensor. Then take the shot again to see if it's now clean.
09-18-2008, 11:38 AM   #6
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BTW, I got a sky shot which definitly shows dust spots. But I also tried the dust alert system just to see against a perfect white screen and it shows nothing. I assume it just isn't sensitive enough.
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