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10-07-2009, 09:26 AM   #1
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dust on sensor or dust on lens

I was doing some boating last night and noticed a few images that indicated some dust on my equipment. Is there a way to tell by looking at the image if the dust is on the sensor or on the lens itself? I can't really tell by looking at the lens or sensor. I don't want to start unnecessarily touching my lens or rocket blowing in the camera body if it isn't in there and end up making it worse?

spec is on the right of the images about 1/2 way down





10-07-2009, 10:03 AM   #2
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Possibly on the sensor. But they don't look that bad to me, not enough to blow into the sensor. I've had a few specs on my sensor, much larger than your's. I resisted blowing into the sensor. I turned on sensor-shake-when-powering-up feature instead, and after a while they've dropped off.

BTW, shoot against a clear, cloudless sky, stopped all the way down. That way you can scan the entire sensor for dust, unlike in the attached pics.
10-07-2009, 10:06 AM   #3
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Dust on the lens WILL NOT show up on the image as a visible artifact.
If you can see it on the image you have dust on your sensor.
10-07-2009, 10:29 AM   #4
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Thank you. I guess I will just live with this for now even though every time I look at it it is like nails on a chalk board. Oh, I did the clear sky thing and I found a few more specs. Damn!

10-07-2009, 11:01 AM   #5
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QuoteOriginally posted by Wheatfield Quote
Dust on the lens WILL NOT show up on the image as a visible artifact.
If you can see it on the image you have dust on your sensor.
This makes sense, but what effect does dust / particles on lens front element as well as rear element do? loss of contrast in an area?
10-07-2009, 12:07 PM   #6
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As an aside to the other answers, the one thing that you can do to confirm a lens vs. sensor question is to see what happens once you swap lens. If it is the sensor, you should get the same dust spots no matter what lens (although their sharpness and size will vary with aperture).
10-07-2009, 12:55 PM   #7
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QuoteOriginally posted by Eruditass Quote
This makes sense, but what effect does dust / particles on lens front element as well as rear element do? loss of contrast in an area?
Loss of contrast or loss of sharpness if there is an extreme amount of dust on the lens.

QuoteOriginally posted by emalvick Quote
As an aside to the other answers, the one thing that you can do to confirm a lens vs. sensor question is to see what happens once you swap lens. If it is the sensor, you should get the same dust spots no matter what lens (although their sharpness and size will vary with aperture).
Unless the plane of focus is actually inside the lens on one of the lens elements, you will not see dust on the lens as a visible artifact on the image. Changing lenses will tell you nothing, since if the spot is visible, it is not on the lens.
There will be the very rare circumstance where the plane of focus is so close to the front element that dust might be visible if one is doing extreme macro work with the wrong lens, but in normal picture taking situations, lens dust will cause little or no visible image degradation, and what it does cause will not be visibly apparent (spots on the image).
10-07-2009, 02:06 PM   #8
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QuoteOriginally posted by 41ants Quote
Thank you. I guess I will just live with this for now even though every time I look at it it is like nails on a chalk board. Oh, I did the clear sky thing and I found a few more specs. Damn!
No reason to just live with it. Run the dust removal a dozen or so times if you camera has it; if that doens't take care of the problem, go into sensor cleaning mode and blow the dust off with a "rocket blower" or something similar (google will tell you all you need to know about that).

10-07-2009, 10:00 PM   #9
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QuoteOriginally posted by Marc Sabatella Quote
No reason to just live with it. Run the dust removal a dozen or so times if you camera has it; if that doens't take care of the problem, go into sensor cleaning mode and blow the dust off with a "rocket blower" or something similar (google will tell you all you need to know about that).
This works best, I find, with the lens mount toward the floor to take advantage of gravity. I also have turned on the shake every time I start the camera dust removal system. I've never had a serious dust problem.

I do change lenses very carefully, and with the lens mount down in the hopes that the dust won't fly up into the camera body. I never change lenses with the camera powered on. I believe that the change on the sensor may attracct dust.

Last edited by Canada_Rockies; 10-07-2009 at 10:06 PM.
10-08-2009, 08:30 AM   #10
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QuoteOriginally posted by Canada_Rockies Quote
This works best, I find, with the lens mount toward the floor to take advantage of gravity. I also have turned on the shake every time I start the camera dust removal system. I've never had a serious dust problem.

I do change lenses very carefully, and with the lens mount down in the hopes that the dust won't fly up into the camera body. I never change lenses with the camera powered on. I believe that the change on the sensor may attracct dust.
I don't know if one can rely on gravity too much when it comes to dust. It's more like terminal velocity, and a very slow one at that.

There is usually dust right at the camera/lens mount. I always wipe and blow that area first to avoid dust entering into the cavity once the lens is removed.
10-08-2009, 10:28 AM   #11
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Dust on the sensor becomes much more visible when you work with small apertures (high f numbers). Put your camera in Av mode, choose the smallest aperture f22 or higher, take a picture of the sky. You'll notice it immediatly.

My personal experience is as follows:
- Sensor dust removal on my K10D works somewhat, I have it on when powering up the camera. Still now and then I need to clean the sensor.
- The K-7 dust remove shaking system is much more effective. No need for cleaning and I'm changing lenses all the time.

A rocket blower (plus gravity) works in 80% of the times. For the rest of the problems I use wet and dry swaps, expensive but very effective.
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