Old 20-11-2009, 04:00 PM
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erick (Eric)

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Photography - Kinder

Be patient, please. I need help.

So I took RAW photos of the fog (was supposed to be a meteor shower?). I have several hundred of them. Shot on a Pentax K100D, they are in Pentax's PEF format and are about 11MByte each. I also covered the lens at the start and at the end and took around 10 darks each time. Shooting for 30sec @ ISO 800.

Point 1: Boy, my chip is noisy (see attached) - but I had already gathered that would be the case from what I have read. So this is about learning some procesing basics, not producing quality images!

Point 2: How do I process? I gather I need to average the darks, then subtract from a light and see what happens. But how? Pentax software doesn't seem to have anything useful. I have added the plugins so I can open PEF files in Irfanview. I also have the Adobe convertor and have converted some into DNG files (they are about 5-6MByte compared to the 11MByte PEFs). I have Photoshop Elements (PE), but cannot see options there for averaging images. Also I cannot see how to open PEFs or DNGs in PE. It asks me for lots of information about the file - pixel width and height I can supply but "interleaved" etc?

So any handy hints for the uneducated photographer would be gratefully received. I cannot anything in the "Articles" to help me.

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Old 25-11-2009, 10:35 AM
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StephenM (Stephen)
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Hi Eric,

I also have a K100D, and have recently been attempting some star trails. I've also discovered how noisy the Pentax chip is! When doing a series of repeated 30 sec exposures, it starts off with minimal noise, but after about 10 or 15 consecultive images the noise rapidly builds up (as in your image) . So try and limit it to 10 shots at a time, and then let the chip recover for a while. Here is an example of 10 stacked 30 second exposues with darks subtracted:


With respect to the processing, however, I've found that Deep Sky Stacker handles the Pentax RAW format, and the results are much better with RAW files than with extracted JPGs.

Hope this helps.

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Old 25-11-2009, 11:11 AM
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erick (Eric)

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Thanks, Stephen - I saw exactly the same. Started up the camera, took 10 successive darks, the noise built from a few speckles in the first to significant coverage of the frame from about 5 or 6 onwards!

Back to my original question - the answer is Deep Sky Stacker? OK, I'll go looking for that.
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