K5 Dust Alert test?!


armadillo

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Jan 30, 2006
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#1
When first time got my K5, I did dust alert test, seem perfect.
But recently when try again hv something like below sample.
I think just realize, after taking previous shot will effect the dust alert :dunno:
Anyone encounter this problem?



after this image was taken:
 

night86mare

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Aug 25, 2006
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#2
sorry, i am not sure how the previous shot is affecting...

did you take the dust alert picture with white bg
 

fengwei

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#3
Sensor dust is something we have to live with for digital SLR cameras. Just have it cleaned or clean it yourself :)
 

jjynwa

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Nov 9, 2007
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#4
Those squarish things seems to be the spotlights? How did you do the test? Try doing the dust alert test with a plain white background, tripod at maybe f16. If its troubling you, just visit Kevin. :)

Good luck!
 

Last edited:

armadillo

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#5
I'm using the internal camera dust alert test.
Also did the same test, after taking normal shot, seem no dust after that.
The conclusion, dust alert is not 100% accurate :think:
 

night86mare

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#6
dust alert needs a white bg.

if you are shooting a scene with those shapes present, then naturally the camera will give you that result,.
 

armadillo

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#7
Ok, make sense, tonight will try again to shoot white bg, and test the dust alert, to see if same problem.
 

night86mare

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#8
Ok, make sense, tonight will try again to shoot white bg, and test the dust alert, to see if same problem.
oh, no wonder you are getting those shapes.

i think it is in the manual that you need to have white bg...

basically what the camera does is (you need af):

(1) stop down to f/16, adjust via af to min focusing distance (probably to throw every detail on the white wall, if it is not that white oof)

(2) take photo, and then proceed to process it to have high contrast to highlight where the dust is

to be honest, dust alert will only detect larger pieces of dust because you can't really zoom in.

the best way to test for dust is to do the same thing yourself, and set it to f/22, and then zoom in at 2x. anything only visible at larger magnification is not that significant and will not be noticeable, or if noticeable, very easily cloned out.
 

armadillo

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Jan 30, 2006
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#9
bro night86mare, thanks for the great info :thumbsup:
that is why in some occassion when I use dust alert, looks 100% clean.
so, shoot white bg b4 dust alert, is the key :)
 

Gengh

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May 6, 2007
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#10
bro night86mare, thanks for the great info :thumbsup:
that is why in some occassion when I use dust alert, looks 100% clean.
so, shoot white bg b4 dust alert, is the key :)
No no, it has nothing to do with the picture you shoot before using dust alert. When you're using dust alert, you have to point it at a plain, featureless bg as you press the shutter. In fact, you want the picture to be as OOF as possible, so it works best if you go close to a white wall to do this. Dust alert automatically focuses at infinity.
 

Nov 15, 2008
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#15
I think you totally mis understood how to do a dust test.....

First you take off your lens cap.
Next you look for a white wall,paper, anything that when you view thru the viewfinder is all white.
Next you go to the menu---->dust alert---->select it and cam will prompt you to press the shuttle to do the dust test
Cam will set the aperture to F16 automatically
So next you look thru the viewfinder again, confirm what you see is all white
press the shuttle
This is so the image next shown,anything that is not white is dust......
 

armadillo

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Jan 30, 2006
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Pinnacle@Duxton
#17
Ok, thanks for the info, I think to clear my doubt tonight will try again, above mention method :)
 

armadillo

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Jan 30, 2006
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#19
Just test again, with my lens cover, result is 100% white, no spec of dust at all.
I think doesn't matter what you shoot, as long you leave the camera idle for few minutes before you do the dust alert test, that will work.
Or if you can't wait then just shoot any white background, that will work as well :)
 

Last edited:
May 7, 2010
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#20
I think you totally mis understood how to do a dust test.....

First you take off your lens cap.
Next you look for a white wall,paper, anything that when you view thru the viewfinder is all white.
Next you go to the menu---->dust alert---->select it and cam will prompt you to press the shuttle to do the dust test
Cam will set the aperture to F16 automatically
So next you look thru the viewfinder again, confirm what you see is all white
press the shuttle
This is so the image next shown,anything that is not white is dust......
thumbs up for this.

Many people misunderstood how sensor checks for dust.

this should clear things up...
 

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