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01-26-2011, 11:27 PM   #1
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Dust Alert

Just wondering if someone can tell me how this feature is supposed to work...

I noticed "mark" on the bottom of a few photos I took tonight, so I ran the dust alert function and it showed a filthy... VERY filthy sensor. I had the lens pointed towards the lights in my kitchen. Then I used the sensor cleaning option in the menu and after the camera shook, the sensor showed even dirtier!

Then I tried pointing the camera at the TV and running the Dust Alert.... no dust.
At the kitchen light... filthy.
At a desk lamp... minor dust.
At the computer screen... light dust.
At the kitchen... very filthy.
At the computer... horizontal lines of dust.

Anyways, all my tests come back randomly different... any hints?

01-26-2011, 11:53 PM   #2
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I believe a clean, light colored wall inside and either clear blue sky or flat overcast outside are the best surfaces to use. A diffused consistent light from edge to edge will show you what is really there.

Good luck!
01-26-2011, 11:55 PM - 1 Like   #3
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The dust alert is only mildly useful. It is very easily fooled by camera movement, objects in the frame (moving picture on your television), stationary objects in your frame, etc. Point it at a plain, blank wall or a simple piece of monotone paper. Trust your photos. Stop your lens down as far as it will go and take a photo of the sky. Any dust that is going to show on the rest of your photos, will show in that case.

https://www.pentaxforums.com/forums/pentax-dslr-camera-articles/121739-those-...ur-photos.html

01-27-2011, 01:13 AM   #4
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I didn't know one could point a lens at the ceiling and see dust on the sensor through the viewfinder.

Are you sure it's not something on the viewfinder and not the sensor? Or is the K-5 different in viewing dust?

Or did I misunderstand something that was said?


Last edited by photolady95; 01-27-2011 at 01:47 AM.
01-27-2011, 07:38 AM   #5
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PL, Your K100d doesn't have the dust mapping feature. I think it was first introduced on the K20d. What the camera does is basically take what amounts to a completely blown out photo, with the lens fully stopped down (it only works with A type or later lenses). Then shows a photo with the lens mount superimposed so you can see where the dust lies on the sensor. The problem with it is that it is very easily fooled as I mention in my other post.

01-27-2011, 09:57 AM   #6
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I'll have to give this another shot, pun intended

Indeed, the K100d does not have a dust alert or sensor shake.
01-27-2011, 10:01 AM   #7
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Both of you, Jeff and calculator, misunderstood my point in my post. I wasn't asking about my k100d. I was asking if you took photos when you pointed the camera against the ceiling, or if you just pointed the camera at the ceiling and was seeing dust as through the viewfinder.

I know my camera doesn't have those features. But perhaps my next one will have.
01-27-2011, 10:10 AM   #8
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I noticed I had one big spot when I was doing some shooting outside (showed up easily on the snow background)

After I got home, I was unable to replicate the speck, so I'm assuming I had something on the lens itself. However, I shook the sensor and ran the dust alert a few times anyways.

I just tested the camera by running Dust Alert at my lit wall, shows nothing. Actual pictures show nothing. Ran Dust Alert again, but unlit the wall, now I have a filthy sensor. So the verdict is... I don't think I can trust the Dust Alert function.

01-27-2011, 10:24 AM   #9
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Photolady,
stop the lens all the way down and take of photo of something like the sky or plain wall.
Then examine this photo on your computer screen. Any dust spots should show up pretty easily when you zoom in just a bit.

Good luck,
Sam
01-27-2011, 11:17 AM   #10
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Sam I've had my k100d for over a year now. Yes, I know how to see dust is on my sensor. But I wasn't asking for me and no one seems to understand what I asked about in my other posts.
01-27-2011, 11:52 AM   #11
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Sorry PL, I did misunderstand your question. Indeed if you are seeing dust in the viewfinder, it is not on the sensor, regardless of what you are pointing the camera at. As you already know, you must take and examine a photo to see the sensor dust. Don't fret about (I know you aren't) no dust alert. It's so finicky that it's a bit of a useless feature anyway.

01-27-2011, 11:58 AM   #12
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Finally got it did ya? LOL Reason I was asking is what he said in his first post about pointing the camera where he did:

QuoteQuote:
Then I tried pointing the camera at the TV and running the Dust Alert.... no dust.
At the kitchen light... filthy.
At a desk lamp... minor dust.
At the computer screen... light dust.
At the kitchen... very filthy.
At the computer... horizontal lines of dust.
since he can't see the sensor through the viewfinder, my question was, was he taking photos to show the dust on the sensor, not just looking through the viewfinder.
01-27-2011, 11:45 PM   #13
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I was running the dust alert for each test, not just looking through the viewfinder... as that would be useless
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