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Old 25-07-2008, 02:32 AM
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leinad (Dan)
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Purple pixels... help?

I was taking some first-light 30sec unguided test shots out the back tonight with the 18-55IS EF-S, F/8(too high I think) @ ISO400 & ISO800; and I noticed in photoshop these purple pixels.

Can someone help explain what this is? With normal photos I dont see them. I didnt try shorter sec. exposures at the time, so Im wondering if this was because of the 30sec shots.
Anyone had this before?

EDIT: I read I need to take darkframes to reduce hot pixel/noise. Can 350D's do this automatically? Would these be hot pixels?
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Last edited by leinad; 25-07-2008 at 03:01 AM.
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  #2  
Old 25-07-2008, 05:00 AM
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iceman (Mike)
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You got it - they're hot pixels. They don't show up in normal point and shoot shots - they appear in long exposures and with higher ISO.

And you're right - that's what dark frames are for. Either use ICNR or separate darks.
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Old 25-07-2008, 11:50 AM
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leinad (Dan)
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Sorry Mike, what ICNR ?
Must dark frames be done after shooting or during shooting? Can you snap; take dark, snap; take dark..etc, etc or must darks be taken at the pc?


Quote:
Originally Posted by iceman View Post
You got it - they're hot pixels. They don't show up in normal point and shoot shots - they appear in long exposures and with higher ISO.

And you're right - that's what dark frames are for. Either use ICNR or separate darks.
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  #4  
Old 25-07-2008, 12:10 PM
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Tandum (Robin)
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In Camera Noise Reduction. Should be under custom functions in the menus. You take a shot and the camera takes another, of the same exposure time, with the shutter closed and does a dark subtration inside the camera.
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Old 25-07-2008, 12:36 PM
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leinad (Dan)
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Thanks! I'll have a thorough read through the manual tonight, and more on-line reading.


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  #6  
Old 25-07-2008, 06:39 PM
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Omaroo (Chris Malikoff)
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Clone tool in Photoshop... ? It's not exactly a huge problem here...
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