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08-06-2016, 09:59 PM   #1
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Pentax K-1 Showing alot of Hot Pixels using AstroTracer

Hi,

First time using Pentax and trying the AstroTracer with the 15-30 mm lens for 3 minutes @ 15mm ISO 400. If you look in the shadow areas there are alot of hot pixels. Taken on a 80 degree night.Is this common for Pentax?

Here is a link to the file from DropBox.

https://www.dropbox.com/s/go5fuhauhqgs5b1/IMGP0154.DNG?dl=0

08-06-2016, 10:13 PM   #2
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Sounds related to this thread:

https://www.pentaxforums.com/forums/190-pentax-k-1/327326-k-1-white-dot-issue.html
08-06-2016, 10:16 PM   #3
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Did you run DFS / slow shutter speed noise reduction?

Adam
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08-06-2016, 10:30 PM   #4
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At 80 deg F for 3 minutes, yes, this is a normal amount of hot pixels. A cooler sensor and/or shorter exposures will have fewer of them. I loaded your supplied image into my raw editor of choice and it removed them all easily.

08-07-2016, 01:28 AM   #5
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Turn on dark frame subtraction (on the image provided it is off), if those effects are not liked.

But more importantly: Consider changing the aperture from F11 to something a little more supporting low light. It's a F2.8 lens you use.
08-07-2016, 02:55 AM   #6
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It's way to many in my opinion, but maybe that is the way it is with the K-1.
I have never seen anything like that with my K-5 though, on the other hand it is usually colder when I do long exposures, but 25 degrees C (which the exif reports) isn't exactly an extreme temperature either.

I would like to se more examples from other K-ones. Does all have this problem, or is it only early models, or is it later models only?
08-07-2016, 03:17 AM   #7
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Mine was manufactured in March and has them too, but I'm not fussed about them at all.. I like some grain sometimes and they're really not that hard to remove.
08-07-2016, 03:24 AM   #8
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Mine is the first shipped model, I tried editing it in Adobe Raw and it didn't take them out. I didn't check dark frame subtraction.

08-07-2016, 03:47 AM   #9
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Rawtherapee seems to remove them easily, but IMHO they should not be there in the first place. Atleast not the white ones, what are they?
08-07-2016, 04:43 AM   #10
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Here are my settings on the camera I even see the white dots in shadows when I lift exposure on my Pentax raw files. I have some at iso1600

---------- Post added 08-07-16 at 07:55 AM ----------

Here is another shot for download
https://www.dropbox.com/s/afwyose994jwweo/IMGP0147.DNG?dl=0
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08-07-2016, 06:01 AM   #11
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You might want to try running Pixel Mapping in the settings menu. This checks the sensor for defective pixels so that the camera can compensate for them. It won't completely address the problem (and may have no effect on RAW output) but it will help get rid of the more prominent hot pixels (the camera will interpolate around the bad pixels instead).

A more advanced approach is to take a dark frame yourself (long exposure, lens cap on, viewfinder covered to block stray light) and use it in post to correct for the defective pixels. RawTherapee supports loading a dark frame for this purpose.

Draco

Last edited by bwDraco; 08-07-2016 at 06:08 AM.
08-07-2016, 10:06 AM   #12
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Pixel mapping is exactly that. It will take out the stuck pixels by mapping to the next pixel, but only those that show up in normal exposure shooting. So, the format output selected has nothing to do with it.
08-07-2016, 10:26 AM   #13
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I just did a quick scan, and I only saw one (down in the tree area). How many are there? I assumed that everything in the sky was a star.
08-07-2016, 01:51 PM   #14
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I never checked for dead pixels. Will do the pixel mapping. I figured ed since it was new I wouldn't have this problem. I only took less than 200 shots with it.
08-07-2016, 02:58 PM   #15
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Again: Turn on the long exposure noise reduction, which you seem to have set to off currently. It is there for exactly this type of application.

You may want to read the section "Dark Stability" in this long article here: Profiling the Long-Exposure Performance of a Canon DSLR - Fishing for Photons - Articles - Articles - Cloudy Nights which is mainly about how Canon pre-cooks their raws, but that chapter with the two raws shows what is happening in all cameras during long exposures.

Here is also some interesting read on the "big white pixels" showing up on the recent 6D:
Why is my 6D Long exp. noise reduction giving MORE noise? (pics inside)
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