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Old Jun 18, 2008, 12:52 AM   #1
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I'm peeved! I took a few shots of Mystic River at dusk last weekend and I thought that I wouldnt have a problem since I put the K100 on the tripod. I kept the ISO at 400 so I could cut down on noise and took this picture that was a 10 sec exposure. Problem is when I came back home to look at it I saw all of these hot pixels and noise in the shot. I guess 10 seconds is too long a time? I know there's a term for digital noise in long exposure shots but it escapes me right now.

What do you think should be the longest for the shutter to remain open? I'd like to keep the ISO relatively low to cut down on noise but I'd gladly take the noise at 1600 then what you see in the picture!

Its a shame too because I really like the shot but I doubt any PP can fix this. :sad:

Thanks for any help.


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Old Jun 18, 2008, 4:00 AM   #2
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Hi, How's this ... In PS Iran this filter ... Filter/Noise/ Median @ 2 pixels, then used Hi pass filtering to restore the sharpness, only took a few minutes. I could probably be refined more if I spent more time on it. ... Jack

Edit ... the sharpening has produced a halo effect, it was a rush job though, I didn't have time to play with it long.
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Old Jun 18, 2008, 5:56 AM   #3
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You might check some of the photo astronomy sites. They will give procedure for correcting long time exposures. Consists of taking equal time dark frame and subtracting with appropiate software. Also, is your camera firmware up to date? Similar problem on K20D has a firmware fix????? I have previously done much longer exposures with my DS and no problems.

cheers

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Old Jun 18, 2008, 9:06 AM   #4
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I have taken much longer exposures that this with my K100D without anything in them that looked like this.

I always shoot raw and the raw converter eliminates the few hot pixels automatically. I would also not up the iso for a static long exposure on a tripod. That is liketurning up the gain that can lead to more noise itself.

And, the camera will automatically do the dark frame subtracting, also, further elimintaing noise and hot pixel issues.

Dennis
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Old Jun 18, 2008, 10:42 AM   #5
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Not too bad, Jachol. It looks like an impressionist painting now. :-) I have to see if I can do it without losing a lot of the detail. Thanks.

Also, a couple of things I know for sure:
1) The firmware is up to date.
2) The ISO was 200 on that pic. The next couple were at 400 so I can cut the exposure time down from 30 sec to 13 sec.
3) I didnt use RAW, I used 6MP jpeg. It got me thinking tho, am I better of using RAW for shots like these? Its my first time doing more than 2 sec shots with the k100.
4) Noise reduction is turned ON in the menu.


but I'm not exactly sure however if I turned of the Shake Reduction when it was on the tripod. But it wouldnt have that effect, would it?

I appreciate the help.
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Old Jun 18, 2008, 3:02 PM   #6
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Yes, you are better off using raw. Raw convertersmap out the hot pixels from the image.The Pentax Photo Lab software that came with the camera will do this.

As forSR, I usually use the 2 second timer when shooting long exposures on a tripodwhich turns SR off automatically and utilizes mirror lock up to limit vibrations.

Dennis
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Old Jun 18, 2008, 3:32 PM   #7
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I have to start using the Pentax software. I've been using Lightroom for the past year. I was turned off to it because it wasnt as user friendly as Lightroom but hey, if it works better... :idea:
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Old Jun 18, 2008, 4:12 PM   #8
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I don't use Lightroom but everyone raves about it. I think you can use Adobe Camera Raw (ACR)with Lightroom and it will do what I'm talking about, too. Lightroom has to be WAY friendlier than the Pentax software, which is notoriously unfriendly!

I just mentioned PPL because of the raw converter in it.

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Old Jun 18, 2008, 7:30 PM   #9
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Hi,

Never mind. The edit turned out better on my screen....

Rudy
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Old Jun 18, 2008, 10:47 PM   #10
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I like the last edit - worked quite well. Lightroom will automatically eliminate hot pixels on raw files. I know this because my computer is pretty slow and when it takes a while for Lightroom to create the previews. Until it does, it shows the uncorrected file and the last couple of days I saw one hot pixel in my shots. As soon as LR came up with the preview it disappeared.

I'm not sure what you have in your original are hot pixels - it looks different than the bright dots I've seen that are hot pixels. The funny thing is that I got something sort-of similar once when I was shooting a very back-lit scene of yuccas early one morning. I just thought it was dust and pollen blowing around in the air, reflecting the very early morning sun. I first thought it might be the K20's random hot pixels that were being talked about, until I realized the picture had been taken with the K100.
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