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09-14-2006, 01:17 PM   #1
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white dots

I purchased the Pentax ist DL May 7 of this year and love it. Lately my pictures are covered in little white dots, only noticable at high resolution and usually only against a blue background, like sky, etc. At first there were only a few dots, which are always in the same place on all pictures. I thought this started happening about a month after I bought the camera, but checked the first pictures I took and they are on them as well, but only a few. Now there are at least a couple of dozen. If you blow up the pictures, the dots appear as plus signs. I have cleaned the lens and filter to no avail. I read the post about hot pixels, but do not beleive it is the same issue. I have attached a test pic shot against the side of a blue vehicle. The white dots are visible througout. I tried the same shot in manual focus, 200 ISO against the lens cap, but there weren't any dots. I have also disabled the noise reduction and tried several pictures and all show the same white dots.
I wrote to Pentax tech support this morning, but as yet have not had a response to my query.
help, they are ruining my pictures.
Any suggestions.

thank you
A

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Last edited by digital diva; 09-14-2006 at 02:32 PM.
09-14-2006, 01:50 PM   #2
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Look like hot/dead pixels...

Hi A!

Those do look like hot pixels or dead pixels. When you did the lens cap shot, how long did you do the exposure?
09-14-2006, 02:31 PM   #3
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white dots

Thanks for the reply Tracy. I held each exposure with the lens cap on between 8 to 10 seconds. None of the black shots show any white dots, only when shooting against a blue sky, background, etc. I also just blew dust off the CCD and tried again, but the dots are still there and in the same place.
09-14-2006, 02:54 PM   #4
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QuoteOriginally posted by digital diva Quote
Thanks for the reply Tracy. I held each exposure with the lens cap on between 8 to 10 seconds. None of the black shots show any white dots, only when shooting against a blue sky, background, etc. I also just blew dust off the CCD and tried again, but the dots are still there and in the same place.
Hi again!

Because I'm interested in astrophotography, one of the first things I did when I got each of my DS bodies is to run a hot pixel test on them using a program you can get here:
http://www.starzen.com/imaging/deadpixeltest.htm

I turned ON (sorry, I previously said off but meant on) noise reduction, got into a completely dark room, put on the lens cap and the eyepiece cover (not the eyecup, the cover so it's completely covered) and did 30 second exposures at 200, 400, and 800 ISO. Try that. If the white dots are showing up in the exact same place everytime then it's most likely stuck/hot/dead pixels. This software will give you mappings to the exact coordinates of the pixels. Run several exposures at the same ISO so that you can rule out random noise problems.

I averaged no hot pixels at 200 and 400, and then around 3 at 800 and 44 at 3200. What's weird is that none showed up at 1600. It was a result I could live with and 'heal' with Photoshop.

I'm really sorry you're having these white dots. That's aggrevating to find in a relatively new camera, I know. If it's only 12 or so, I personally wouldn't worry and just fix them in post processing. But if it's really irritating you, you send the camera in for servicing. Then you'd be without a camera for a few weeks, though.

09-14-2006, 03:05 PM   #5
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white dots

hi again Tracy,

I will try your test with noise reduction on and off. I will also try the link you suggested. I tried a program 'hotpixels' today to remove them, but found it didn't work at all.

I have been reading up as much as I can on other forums and each is suggesting hot pixels, and says all cameras have them, some more than others. I am awaiting a reply from Pentax regarding sending the camera in for repairs. If it was only a few white dots, I could live with it, and fix in photoshop. However, there are far too many to fix without compromising the quality of the proof which I cannot afford to happen.

thanks again and I will let you know how the test turned out.

Annette
09-14-2006, 03:29 PM   #6
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white dots

Okay, I downloaded the dead/hot pixel program. I shot four pictures, ISO 200, 400, 800 and 1600 in Jpeg format, even though that is not recommended. I cannot shoot tiff, and the test program does not recognize pentax raw image data. There were no dead or hot pixels at 200 ISO/30 second exposure. At the 400 and 800 it recorded 6 hot pixels, 0 dead pixels. Aat 1600 ISO 0/0 for both. I could only see them myself in irfanview viewer program in two of the test pictures.
Also, they are not in the same place that the white dots occur in my other scenery photographs.

Annette
09-14-2006, 04:06 PM   #7
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thanks for the tip, photo_mom

QuoteOriginally posted by photo_mom Quote
Hi again!

Because I'm interested in astrophotography, one of the first things I did when I got each of my DS bodies is to run a hot pixel test on them using a program you can get here:
http://www.starzen.com/imaging/deadpixeltest.htm

I turned ON (sorry, I previously said off but meant on) noise reduction, got into a completely dark room, put on the lens cap and the eyepiece cover (not the eyecup, the cover so it's completely covered) and did 30 second exposures at 200, 400, and 800 ISO. Try that. If the white dots are showing up in the exact same place everytime then it's most likely stuck/hot/dead pixels. This software will give you mappings to the exact coordinates of the pixels. Run several exposures at the same ISO so that you can rule out random noise problems.
That's a great tip! Thanks for sharing.
09-14-2006, 04:45 PM   #8
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solutions to hot pixel problem

These are dead or hot pixels, made more visible by the jpg conversion.
Pentax can map them out (should be free under warranty) so that you don't see them but as the sensor gets older, more will probably develop.

One cure is to shoot RAW and use Photoshop CS2's RAW converter which will eliminate the hot pixels. Photoshop is expensive, though. A more cumbersome solution is an inexpensive program called FlameOut:

http://www.gold-software.com/download6128.html


Last edited by Ole; 09-14-2006 at 04:54 PM.
09-14-2006, 05:27 PM   #9
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QuoteOriginally posted by digital diva Quote
Okay, I downloaded the dead/hot pixel program. I shot four pictures, ISO 200, 400, 800 and 1600 in Jpeg format, even though that is not recommended. I cannot shoot tiff, and the test program does not recognize pentax raw image data. There were no dead or hot pixels at 200 ISO/30 second exposure. At the 400 and 800 it recorded 6 hot pixels, 0 dead pixels. Aat 1600 ISO 0/0 for both. I could only see them myself in irfanview viewer program in two of the test pictures.
Also, they are not in the same place that the white dots occur in my other scenery photographs.

Annette
Hi Annette!

You can get TIFF files by shooting RAW and then converting to TIFF. That's what I did using the BibblePro converter. But the PENTAX Photolab software should do the same. I think with the compression in JPG might affect the test results. But someone who knows more about JPG compression would have to answer that.

Sorry I couldn't help more. Ole had a good answer, though!
09-14-2006, 05:29 PM   #10
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You're welcome! But...

QuoteOriginally posted by uccemebug Quote
That's a great tip! Thanks for sharing.
Hi Michael!

I can't take credit for the tip. I got it from THW and Richard Day on dpreview back when I first got started. I'm just passing it on. Hope it helps!
09-15-2006, 03:39 PM   #11
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white dots

Just want to thank you all again for your suggestions.
I have downloaded Flameout and tried to use it to fix the white dots, but it didn't work either. I have again taken a series of lens cap/total darkness pictures at ISO 200 - 1600 in RAW format. I converted them to Tiff files to run them through deadpixeltest. The program did not find any dead pixels and only identifed a max of 6 hot pixels in two of the exposures (400 and 1600 ISO), virtually the same result as with the earlier test pictures taken in Jpeg format. The hot pixels it identified are not in the same place where the white dots are showing up on my images, and as mentioned, there are now at least two dozen per image, not just 6. The white dots are in the same position regardless of which lens I use on the camera.
I still have not had a response to this issue from Pentax. I will be sending the camera to Pentax for repair. If I ever find out what the problem was, I will certainly report it in the forum.

Any suggestions how to ease my withdrawal sypmtoms from not having my camera attached to my hip every day while it is at the shop? lol
09-15-2006, 06:11 PM   #12
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If it isn't hot pixels then maybe either manufacturing flaws on the filter covering the sensor or perhaps damage from someone mishandling the camera before you got it. Since the dots are always in the same space they *must* be sensor related.

What about an Optio WPi to carry you over the hump? It can later come in handy in places where you wouldn't bring your DSLR!
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