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03-24-2009, 06:38 PM   #1
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Sensor Dust or what???

I am new to DSLR's and the K20d was my first one. I love the camera and have done fairly well using my own settings etc...I have had the camera for about 3 weeks now and have noticed some "artifacts" on my images once downloaded to my computer. They show up on every image in the same spot, but not every time. I could expose the pictures the same on similar backgrounds and sometimes it shows up and sometimes it doesn't.

I am thinking it may have to do with the lens and not the sensor as I have done dust removal a bunch of times to remove any particles.

I leave the lens cap on when doing dust alert to see if any particles show up. Is this how your supposed to do it? or do you have recommendations?

Could you please help me understand what is wrong? I will attach an image below with a good representation; the artifacts are in the right hand side of image above the car.

FYI: I have had a filter on the lens since i purchased it

03-24-2009, 08:36 PM   #2
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If it shows up when you have high F-stop (F16, F22 etc.) but not when you have them low (F1.8, F2.2, etc.), then most likely it's sensor dust. Do you have any other lens to try on to rule out junk on your lens? (I doubt that's the issue, as it would have to be a fairly sizeable gunk to show up in your images).

For dust alert to work properly, find a nice white wall and shoot at that.
03-24-2009, 08:58 PM   #3
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It's sensor dust. Dust on the lens won't show up in an image.

The Dust alert feature must be shot at either a totally blank sky or a blank wall. Be very careful that nothing falls into the field of view, because it will show up as big, black dust/lint.

Get a Giottos Rocketblower (~$20) and blow out your camera yourself. Don't just get an ear bulb, as all that does is suck dust in through the nozzle and blow it into your camera. The Rocketblower sucks air in through a filter in the bottom and blows it out the nozzle. It's all I've ever used on any of my dSLRs. Never had to do a wet cleaning.

BTW, all dSLRs will get dust, so the Rocketblower will pay for itself very shortly.
03-25-2009, 06:47 AM   #4
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Just Checked my dust alert function and it shows no dust. Do you think this is a lens issue?

03-25-2009, 06:52 AM   #5
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QuoteOriginally posted by NT-Tim Quote
Just Checked my dust alert function and it shows no dust. Do you think this is a lens issue?
It is dust.
03-25-2009, 08:55 AM   #6
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QuoteOriginally posted by rfortson Quote
Get a Giottos Rocketblower (~$20) and blow out your camera yourself. Don't just get an ear bulb, as all that does is suck dust in through the nozzle and blow it into your camera. The Rocketblower sucks air in through a filter in the bottom and blows it out the nozzle. It's all I've ever used on any of my dSLRs. Never had to do a wet cleaning.

BTW, all dSLRs will get dust, so the Rocketblower will pay for itself very shortly.
I'll second the recomendation. I had the same issue last week an jumped on line to order a rocket blower. Best $10 accessory for your DSLR. Here's the cheapest I found it. Rocket blower
03-25-2009, 09:58 AM   #7
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QuoteOriginally posted by NT-Tim Quote
Just Checked my dust alert function and it shows no dust. Do you think this is a lens issue?
You'd be amazed at the size of objects that can be on/in a lens before it will discretely show up in an image. What you're seeing is almost certainly sensor dust.

Also, did you shoot your dust alert shot at a blank wall? Shooting with the lens cap on doesn't work.
03-25-2009, 02:39 PM   #8
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example

This is a crop to show what shows up. this is at f27

Attached Images
 
03-25-2009, 03:06 PM   #9
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That's definitely dust...

The best way to check and confirm as others have mentioned is to shoot at a blank wall or blank sky... Shoot at a high aperture. I usually do f22. Use manual focus and deliberately shoot out of focus. Everything but the dust on the sensor will be out of focus.

Get a rocket blower. It will work most of the time... I say most because until I realized I had dust, my sensor was so bad that the rocket blower was only blowing it around and not out. I had to do a wet cleaning. Ever since then, the rocket blower has worked.
03-25-2009, 07:39 PM   #10
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I have only had the camera for 3 weeks and have never taken the lens off. I have also done 4-5 dust shots and it shows not a speck of dust. I have done it with a blank wall etc... The first shot showed dust but after using the dust removal function a few times the small specks were gone. I looked at the sensor after taking the lens off today and couldn't see even a speck of dust, but I did see what appered to be a smudge of sorts (not of a finger). Could this be the problem? or could it be a lens issue still?
03-25-2009, 08:01 PM   #11
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If you see smudge on the sensor, that's even a bigger problem. How'd dit that get there if the thing was new??

I will jump in and say that my DA 10-17 Fisheye had an ant... yes, the insect, just behind the primary element



And that DID show up in my images at small apertures. Problem for me was that I never shot at small apertures for the first several months of owning it, since I didn't have to; needless to say, I was very surprised when I found out :-)

Since the thing was practically stuck to the lens (as opposed to being loose and rattling around), I figure it must have gotten in during assembly. Vietnam apparently has an ant infestation problem :-)))


Point being, there's no need to rule out the lens. I would still say that the best way to check that is to try with another lens you can get your hands on.


Or, if there's no way you can do it, try this:

Take the lens off, hand hold it in front of your cam, rotate the lens so that it's in a markedly different position that it usually is, and shoot (if it's a fully AF lens, all the better, because it'll shoot at the smallest aperture. Make sure you do it somewhere nice and bright). If you see those specs in different spots, then it would be a lens issue. If they stay in the same places, it's definitely sensor.
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