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10-14-2018, 12:45 AM   #1
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K-1ii white dot issue ?

Being this far north and with constantly cloudy skies I've not had much opportunity to get out and do some night time photography, however I did get an opportunity a couple of nights ago. Looking at an image taken at ISO 2500 for 600 seconds I see hundreds/thousands of bright dots. Reading the forums I have only seen K-1 owners mention the white dot issue and wondered whether any other K-1ii owners are seeing similar. I've attached a 100% crop of a minimally processed image as an example. The dots don't always appear to be single pixels and are not all white, but are distinctively different from the expected noise.

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10-14-2018, 01:43 AM   #2
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In order to get a nice clean gray frame, the 10 minutes exposure would consist of stacking 10 exposures of 1 minute each, with any camera of any brand, or get a lens with larger aperture so that to shorten the exposure time or reduce the ISO setting. That's how most people do for night sky photography.
10-14-2018, 01:59 AM   #3
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I understand about stacking to average out noise, however these white dots are extreme outliers and I don't think normal noise. From what I recall I also tried in camera multiple exposure averaging when I first got the camera and still saw dots. I'd have to look back to check
10-14-2018, 02:35 AM   #4
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I have only found 2 approaches around the white dot issue with my original K1. I've experienced white dots with exposures of 50 sec, ISO 800 @ f2.8 using the astrotracer.
  • Using the in-camera Long Exposure Noise Reduction (LENR) setting - which is essentially dark frame subtraction. This doubles your long exposure with the camera taking a second dark frame to subtract from the first. Or you can take a dark frame manually and in post processing subtract it off (PhotoShop).
  • Use Camera One (C1) for post processing with out using a dark frame. This raw processing utility removes the white dots automagically upon loading the image. I don't know of RAW Tharpee is able to also do this, but LightRoom is not able to remove them.



10-14-2018, 02:53 AM   #5
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I was hoping to avoid LENR because of the additional exposure time, but I understand it is an option for some shots
I process using Rawtherapee, and the impulse noise reduction feature seems to do an excellent job of removing these artifacts. What bothers me is I'm seeing them in the first place. I've not seen similar on the K3 or K30, and thought that perhaps the problem had been fixed on the K-1ii
10-14-2018, 04:08 AM   #6
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QuoteOriginally posted by damianc Quote
I've not seen similar on the K3 or K30, and thought that perhaps the problem had been fixed on the K-1ii
Dark current noise is a fact of all sensors. It is more or less prominent depending on the sensor. Dark frame subtraction has been a regular technique since digital cameras are used, it's not a "problem" of Pentax K1 or Pentax K1 II, it's something we have to consider for the making of night sky photographs. White dots are on the K1 and K1II and all cameras using the same sensor (Nikon, Sony..), they do appear when pushing ISO and exposure time. Ten minutes exposure time is very long... I use 2 minutes exposures at ISO1600 at dark sites , f2.8, means your aperture was f5.6 in the example shot (why no aperture value in the exif?). If you need to expose for 10 minutes, means you have a slow lens for night sky photography, and so stacking multi-exposures is the cheap option at the expense of spending more time for the post processing.

Last edited by biz-engineer; 10-14-2018 at 04:14 AM.
10-14-2018, 04:41 AM   #7
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QuoteOriginally posted by biz-engineer Quote
why no aperture value in the exif?
It was taken with a k35mm at f4 I think. There was a fair amount of atmospheric haze too: I was experimenting rather than looking for a great shot. I do realise I was rather pushing the limits at 10 mins, but wanted to explore those limits.
I've perhaps not read widely enough on the subject, but understood that Nikon had some sort of fix for the d810, I was assuming Pentax had done similar.
10-14-2018, 05:43 AM   #8
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QuoteOriginally posted by damianc Quote
It was taken with a k35mm at f4 I think. There was a fair amount of atmospheric haze too: I was experimenting rather than looking for a great shot. I do realise I was rather pushing the limits at 10 mins, but wanted to explore those limits.
I've perhaps not read widely enough on the subject, but understood that Nikon had some sort of fix for the d810, I was assuming Pentax had done similar.
Well, you know what they say about assuming.
But I'm curious about the Nikon fixes, can you post links?

10-14-2018, 06:00 AM   #9
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QuoteOriginally posted by normhead Quote
Well, you know what they say about assuming
- guilty as accused. Only evidence being no-one on here seems to have mentioned it in relation to the K-1ii

ISTR it's somewhere in the long thread about the white dot issue in relation to the K1. I'll check when I get back
10-14-2018, 12:53 PM   #10
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QuoteOriginally posted by damianc Quote
- guilty as accused. Only evidence being no-one on here seems to have mentioned it in relation to the K-1ii

ISTR it's somewhere in the long thread about the white dot issue in relation to the K1. I'll check when I get back
I have tried the K-1II and can say, that this camera model has white dot noise problem as well as K-1. LENR is the remedy.
10-14-2018, 06:29 PM   #11
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Here are a few links to Nikon's white dot issues. Nikon even had a service advisory on D810 for the white dots.The issue has been discussed here on the K1 too.Here is the best description of the Nikon fix, I can find.
QuoteQuote:
I explored this issue further with Nikon UK (having received their e-mail with the Service Advisory) and established three things:

1. The "cure" consists of altering some of the sensor settings and installing adjusted firmware.
2. There will be no default "cure" in any regular future firmware update.
3. The "cure" will not be total. It will merely reduce the problem.


Last edited by interested_observer; 10-14-2018 at 07:02 PM.
10-15-2018, 03:02 AM   #12
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QuoteOriginally posted by interested_observer Quote
Here are a few links to Nikon's white dot issues
Thank you for that, it saved me the task
The upshot seems to be we have to live with it. Like I stated earlier: Rawtherapee's 'Impulse Noise reduction' does an excellent job of cleaning images up, and coupled with batch processing should make preparation for stacking straightforward. It strikes me that this may be mostly fixable in firmware given how anomolous these pixels are though.

Using Rawtherapee to look at the bayer pattern it looks like (on this image at least) that only green and red pixels are reading high

Last edited by damianc; 10-15-2018 at 03:12 AM. Reason: additional note
10-15-2018, 03:46 AM   #13
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Yes, Rawtherapee impulse noise reduction usually fixes this very well. But not always, sometimes it can end up creating black dots in the middle of highlights as well, and you end up with some sort of craters or donuts. White rings with a black center.
10-15-2018, 10:29 AM   #14
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QuoteOriginally posted by damianc Quote
Thank you for that, it saved me the task
The upshot seems to be we have to live with it. Like I stated earlier: Rawtherapee's 'Impulse Noise reduction' does an excellent job of cleaning images up, and coupled with batch processing should make preparation for stacking straightforward. It strikes me that this may be mostly fixable in firmware given how anomolous these pixels are though.

Using Rawtherapee to look at the bayer pattern it looks like (on this image at least) that only green and red pixels are reading high
I have seen a couple of references to RawTherapee raw processing being one of the best for astro images. I have not read anything on its ability to clean up the white dots on the K1's images though. This would be an additional approach. I currently have the C1 30 day trial, and it does an excellent job - but I like the LR processing better (color rendering) - which is probably not having enough experience with C1. I just ran across this post on the topic today...Overall, LENR fixes the problem, but I would really would rather not double my exposure time on each frame. Taking a dark frame is an option and I'm now doing that as the last frame I take for the evening. The perfect solution is not having to deal with the problem - but at what cost in terms of in camera processing (possibly a repeat of the Sony star eater issues). I'm guessing that Pentax somewhat knew about the problem and just decided that LENR is the solution and let it slide.

I do wish that Adobe would figure out what C1 does and implement a similar approach (processing option). Having the possibly of Raw Tharapee cleaning the dots would be nice, especially since the price meets with the Chancellor of the Exchequer's approval (my wife).

10-16-2018, 07:51 AM   #15
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QuoteOriginally posted by interested_observer Quote
RawTherapee raw processing
I can thoroughly recommend Rawtherapee for RAW processing. It has an incredible number of options, and for me an intuitive layout, though no doubt it may seem different to other tools. Development is very active (I believe it was one of the first tools to offer pixel shift support).
I have tried the impulse noise reduction tool to remove the white dots and it does seem to do a tremendous job, increasing the threshold slider just to the point where almost all dots are removed.
I've not seen the black dots(yet) that Gimbal mentions above: I guess no tool is going to be perfect, but for the money it's definitely worth it - a no brainer on Linux
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