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11-28-2010, 08:01 AM   #1
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Dust spots when using 50-300mm?

Hi,

I just got my new K-x a couple of days ago and I am very happy with it. This is my first DSLR and I am quite impress with the image quality. However, yesterday I noticed that when taking pictures using the 55-300 mm kit lens at maximum zoom (300) there are some dots/line in the image when taking pictures of objects in the sky (see attached pic). I have read other posts related to dust spots and how to clean them, but I want to make sure that these are dusts spots and not a problem with the lens or sensor. Could you confirm that? Should I worry about it?

Thanks

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PENTAX K-x  Photo 
11-28-2010, 09:20 AM   #2
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It does look like dust...try removing it activating the dust removal option several times...you should also check with others lenses. (point the camera at a white paper/object with minimum aperture with different lenses, if you always get those spots its probably dust on the sensor.)
dont worry..they eventually are shook off the sensor (i've had dust and it always comes off with the shaking mechanism..you can activate an option that shakes the sensor each time you turn on the camera, maybe you want to enable it..)
If this still doesn't work you can buy the rocket blower or take it to the shop for a cleaning, when i bought the camera the salesman told me they would clean it for free if i went the first few months
(i'm glad i ain't had the need to, i'm not sure guarantee covers that kind of thing so i'm not sure if he was triying to lure into buying..)
11-28-2010, 09:27 AM   #3
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Was going to suggest there might be a couple of birds up there but on zooming in they are clearly dust spots and there are quite a few more as well and I doubt the Pentax is an exception. Is it the camera or the lens? If it was my camera I'd take it for a good clean!

BTW from your EXIF:
Aperture F/32.0 ISO Equiv. 800
Aperture F/32.0
ISO Equiv. 800

ISO 100 and a bigger aperture would work far better - at f32 most lenses are not at their sharpest and I doubt the Pentax is an exception. There is also little noise in the sky that would go away at ISO 100.
11-28-2010, 11:47 AM   #4
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Spots are caused by stuff on the sensor, not the lens.

Small apertures and plain backgrounds make dust more apparent.

Do not send it in for cleaning. It's easy to do yourself - buy a Giotti rocket blower. For the annual (or less frequent) cleaning, get a sensor cleaning kit.

11-28-2010, 04:52 PM   #5
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I had the same thing happen to my K-X this week. It was my first week using it. The spots persisted with both lenses in my kit, so that left the sensor. I tried shaking the dust off with the dust removal function several times (p.285 in manual) but it didn't work. I ended up raising the mirror up and *carefully* used my Giotti rocket blower to blow the dust off (p.287-288). I had to do it twice and then all was well.
Kent
11-28-2010, 05:18 PM   #6
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QuoteOriginally posted by cats_five Quote
Was going to suggest there might be a couple of birds up there but on zooming in they are clearly dust spots and there are quite a few more as well and I doubt the Pentax is an exception. Is it the camera or the lens? If it was my camera I'd take it for a good clean!

BTW from your EXIF:
Aperture F/32.0 ISO Equiv. 800
Aperture F/32.0
ISO Equiv. 800

ISO 100 and a bigger aperture would work far better - at f32 most lenses are not at their sharpest and I doubt the Pentax is an exception. There is also little noise in the sky that would go away at ISO 100.
One thing I noticed with my K-X out of the box, it would not go lower than ISO 200. With a little research I found that with "highlight compensation" turned off and "expanded sensitivity" turned on, I could get to ISO 100. Whether or not that's a good idea for the OP, I can't say. Just wanted to mention this in case the OP might be as confused as I was about no ISO 100.
Kent
11-28-2010, 07:18 PM   #7
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Dust on the sensor.
For the record, the ONLY way you will see this sort of thing is from dust on the sensor.
Shooting at small apertures (f/32 in this instance) is a very good way to see every bit of grot that has found it's way onto the sensor. Shoot at more moderate f-stops and a lot of your dust problems will go away.
11-28-2010, 09:05 PM   #8
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Hi all,

I noticed that it was also happening with the 18-55 kit lens, so I decided to use the sensor cleaning option in the k-x menu. That didn't work, so I then use the rocket blower and after a couple of tries it worked! Thanks for all the advice.

@kbrede: I didn't know about how to get ISO 100. Thank you for this information!

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