Is there a problem with my sensor?


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stuck

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Mar 12, 2010
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#1
I really started experimenting with some long exposure shots with my K-x & i started noticing this squiggly mark on my photos:

1. 20mm, 10 sec, f/25, ISO 200
in the middle of the right most tower


2. 18mm, 3 sec, f/22, ISO 200
right above fullerton hotel, same spot as #1


Strangely, the mark doesn't appear in my normal shots. For example:

50mm, 1/13 sec, f/4, ISO 1600


Apologies for the poor quality of the pictures! Any ideas? :dunno:
 

mrkumlan

Senior Member
Sep 25, 2009
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#2
i think that's just a piece of dust on your sensor.. nothing to worry about.
 

quackaroo

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#3
I suppose you are using the same lens.

when you shoot at higher apertures (ie: f8 and above) you will tend to see the marks more clearly.
it could be a dirty lens or dirty sensor.

Try cleaning your lens (both sides) of all dust and dirt and point it at a wall or the sky and shoot at f22 and see if there's dust. Change to another clean lens and try.
If those marks appear, most likely they are dust in the sensor.

There are many ways to clean the sensor (you can search the forum to find out).

But recently I had a similar problem. I didnt want to spend the time and money to go down to the Service Center to get it cleaned.
After researching I decided to try a method:
I have a rocket blower.
1. Facing the camera down
2. I removed the lens.
3. Mirrow up, DO NOT TOUCH THE SENSOR WITH YOUR BARE HANDS.
4. Blow air while facing down just at the mount opening. Did it a couple of times in various directions. You do it blind but it's okay.
5. Mirrow down
6. Mount les and Try and shoot at f22 to see where the spots have gone.

You will have to do this in place where it is not dusty (ie: your bathroom!)

It worked for me, may not work for some. If it still doesnt work then send the camera in for cleaning or buy a cleaning kit.
 

night86mare

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Aug 25, 2006
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#4
that's called dust.

google "sensor dust"

you are only seeing it at smaller apertures, where there is greater depth of field.
 

Gengh

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May 6, 2007
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#5
They are dust on the sensor. Dust on the lens will never appear as clear shadows like that, in fact they're practically invisible 99.9% of the time.

Other than the squiggly in the middle, there're 4 other very visible dust spots, three near the bottom edge and one more roughly at the lower 1/3 and right 1/3 spot.

Note that the position of the dust on the sensor is actually opposite of where it shows up on the picture. ie dust shadow on bottom right means dust is on top left of sensor (camera still facing forward). If this is confusing, you can use the dust alert function in the menu and it'll give you a nice picture telling you where the dust is on the sensor.

And on an unrelated note, you probably don't want to be shooting at f22 or f25 unless you have a good reason to, since diffraction effects will set in at such small apertures and reduce the sharpness of the pictures.
 

teodesson

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Dec 29, 2008
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#6
dust on sensor. period.
 

armadillo

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Jan 30, 2006
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#7
I know on K5 you can check the sensor for dust.
Not sure if Kx have :dunno:
 

darrrrrrrrrr

Senior Member
Sep 19, 2006
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#10
that's called dust.

google "sensor dust"

you are only seeing it at smaller apertures, where there is greater depth of field.
don't think it's because of DOF, but because the light is coming in through the lens from a much smaller source as the lens is stopped down, so the shadow cast by the dust particle (which rests on the anti-aliasing glass filter on top of the sensor) on the sensor becomes darker and more defined. with larger apertures, the light can go "around" the tiny dust spot and the shadow is not as visible.

btw to TS, you have more than 1 dust particle on your sensor. at least 4 more on the bottom half of the sensor that i can see in the first picture. not a big deal though, a few puffs and they'll be gone
 

oceanpriest

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Apr 24, 2010
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#11
If blowing still doesn't work, you can try to use wet method. I bought the kit for $30 from Cathay. It comes with 4 swabs.



Or alternatively, you can bring it to emjay ;)
 

stuck

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Mar 12, 2010
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#12
Thanks for all the quick replies & suggestions guys. I must be blind.. didn't even notice the 4 blotches at the bottom till u guys mentioned it! :eek:

I'll try to give the sensor a good once over with the blower & hope it works. btw does anyone know how much would emjay charge to help clean the camera for me if it really comes to that? i'm don't have the most delicate hands... worried that I'll scratch the sensor if i attempt any cleaning beyond the blower myself...

as for shooting at f22... its not the best i know. was just attempting to smooth out the water surface using long exposures (don't own any ND filters) without massively overexposing the shot.

thanks for all the kind suggestions guys... Pentaxians r indeed a friendly and helpful bunch! :thumbsup:
 

darrrrrrrrrr

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Sep 19, 2006
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#13
Thanks for all the quick replies & suggestions guys. I must be blind.. didn't even notice the 4 blotches at the bottom till u guys mentioned it! :eek:

I'll try to give the sensor a good once over with the blower & hope it works. btw does anyone know how much would emjay charge to help clean the camera for me if it really comes to that? i'm don't have the most delicate hands... worried that I'll scratch the sensor if i attempt any cleaning beyond the blower myself...

as for shooting at f22... its not the best i know. was just attempting to smooth out the water surface using long exposures (don't own any ND filters) without massively overexposing the shot.

thanks for all the kind suggestions guys... Pentaxians r indeed a friendly and helpful bunch! :thumbsup:
Try the Multi-exposure mode which lets you average 9 exposures. It functions pretty much like an ND filter by effectively increasing your shutter speed at the same ISO and aperture. It even cuts down noise!
 

oceanpriest

Senior Member
Apr 24, 2010
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#14
I don't know how much emjay will quote you. But one camera repair shop at Adelphi quoted me $30 for cleaning the sensor.
 

Sep 24, 2009
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SG_ID
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#16
....

Try cleaning your lens (both sides) of all dust and dirt and point it at a wall or the sky and shoot at f22 and see if there's dust.

....
one more suggestion is to use long exposure (3-4s), point to bright image (computer screen), and "shake" the camera while taking the picture. this will create blur background and overexposing the image, so that you can see clearly where the dust.. do this again after you blow the sensor to see whether there are any more dust left behind.. (usually there will be one or two stubborn dust left behind, but definitely blowing the sensor properly will reduce the severity of the problem quite significantly..

hope this help!
 

creampuff

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Jul 11, 2006
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#17
bayusuputra, if you move your camera around when taking the exposure, you're just gonna blur the image and any remaining dust specks. Just do a check of the sensor before and after cleaning as explained in the K-x manual.

 

Gengh

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May 6, 2007
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#18
bayusuputra, if you move your camera around when taking the exposure, you're just gonna blur the image and any remaining dust specks. Just do a check of the sensor before and after cleaning as explained in the K-x manual.

Denis, have to disagree with you on this one. Moving the camera around during the exposure will NOT blur the dust spots as the dust will be moving together with the camera. It's actually a very useful technique when using the dust alert function. If the background is not OOF enough, the dust alert can give false positives pretty frequently (I usually use a white wall or door, but the remaining uneveness on the wall or wood grain can sometimes still show up as spots or lines). Moving the camera to generate blurness in the background can solve this problem. Just a slow pan may be enough, depending on the shutter speed used.
 

creampuff

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Jul 11, 2006
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#19
Thanks for the update Gengh. Will give it a try next time.
 

chiangkxv

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Jul 5, 2008
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#20
Denis, have to disagree with you on this one. Moving the camera around during the exposure will NOT blur the dust spots as the dust will be moving together with the camera. It's actually a very useful technique when using the dust alert function. If the background is not OOF enough, the dust alert can give false positives pretty frequently (I usually use a white wall or door, but the remaining uneveness on the wall or wood grain can sometimes still show up as spots or lines). Moving the camera to generate blurness in the background can solve this problem. Just a slow pan may be enough, depending on the shutter speed used.
:thumbsup: thats what i did too.. pretty useful thing to know.
 

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