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08-06-2016, 02:05 AM   #1
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K-1 white dot issue. ?

As reported by Paul2660 and disasterfilm in this thread:
https://www.pentaxforums.com/forums/190-pentax-k-1/323045-milky-way-using-k-1...ml#post3732159

There seems to be a "white dot issue" during long exposures, the same problem that affected the Nikon D810 back in 2013 and resulted in a callback of all bodies to fix the issue. Apparently white dots appears in great numbers during long exposures, it seems to be related to heat as well so it might not appear during the first exposures but as heat builds up they turn up in greater numbers.

Follow the link for examples.

The question is, is this a problem that affects all K-1 released so far?

08-06-2016, 04:03 AM   #2
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I thought the white dots were stars?
08-06-2016, 04:19 AM   #3
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No the faint white dots which show up ip also in areas of non sky per my crop in previous thread are not stars.

They are a form of noise that the chip produces in rather large quantities especially as the chip gets hot.

Capture one software will remove most of them but it's the only raw converter I know of that will. Silky pix and LR cannot remove them.

Paul C
08-06-2016, 04:32 AM   #4
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I guess these dots should appear when shooting long exposures with just the lens cap on? And does the ISO matter?

I ask because I didn't see such a pattern of dots with the K-1 in Brendan Davey's long-exposure camera noise tests:
The Sensor Noise DB. – Brendan Davey Photography

08-06-2016, 04:36 AM   #5
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No evidence of it in this 25 second shot by dpreview (OOC jpeg): https://4.img-dpreview.com/files/p/TS7360x4912~sample_galleries/8034986469/1104076288.jpg

Maybe some stacking effect or it is sensor dependent.
08-06-2016, 04:38 AM   #6
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QuoteOriginally posted by D1N0 Quote
No evidence of it in this 25 second shot by dpreview (OOC jpeg): https://4.img-dpreview.com/files/p/TS7360x4912~sample_galleries/8034986469/1104076288.jpg

Maybe some stacking effect or it is sensor dependent.
That looks cold. If it's a heat issue perhaps the problem isn't showing up when the ambient temperature is sub-brass monkeys.
08-06-2016, 06:17 AM   #7
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Cold temps will definitely make the issue show less prominently. And the longer the individual stack, say up to 1' 30" or 2 minutes, the worse the issue becomes.

If the dots did not look so identical to what Nikon had with the D810, I would have not brought up the issue, but as a night photographer, who stacks, this is a big deal, just as it was with Nikon.

I am not familiar with the previous posters mentioned tests, however if the photographer used the Long exposure noise reduction to "on", the issue will not show for a much longer time frame.

Actually the issue was also in the D800e, but Nikon choose to fix that much more quietly, as early cameras had the problem and later ones did not, per my article. They just somehow forgot the issue with the D810, and got caught sooner, thus did the right thing and fixed it.

D800 Reticulation issues during night photography–white dot problems @ Photos Of Arkansas

The effect is the same, to the letter. Immediately brought back memories of this problem with Nikon, 2012 and 2014 (D800e and D810).

Paul C
08-06-2016, 08:41 AM   #8
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That is very normal behaviour and the very reason why for ages there has been the concept of dark frame subtraction and that is the case for special astro cameras as well.

http://starcircleacademy.com/2012/10/darkframes/
https://www.dpreview.com/forums/thread/3617190

If you want to do it properly you not only have your light frames in raw, but also bias, flat and darkframes - the latter are required per focal length, per ISO, per sensor temperature.

The lazy noob approach is to just switch on the in-camera dark frame subtraction called "long exposure noise reduction". This is automatically at the right focal lnegth, ISO and temperature.

No issue at all, other than lack of user knowledge.

Go to a astro forum and let them teach you, how to approach this.

08-06-2016, 08:55 AM   #9
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QuoteOriginally posted by HopelessTogger Quote
That looks cold. If it's a heat issue perhaps the problem isn't showing up when the ambient temperature is sub-brass monkeys.
That picture of Mt St Helens is taken a bit after midnight on June 26th, according to the Exif. Probably not very warm, but it shouldn´t be very cold.
08-06-2016, 09:51 AM   #10
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QuoteOriginally posted by beholder3 Quote
No issue at all, other than lack of user knowledge.

Go to a astro forum and let them teach you, how to approach this.
So in your opinion any amount of dead, stuck or hot pixels (even though this seems to be something else) is ok as long as it can be fixed with dark frame subtraction? Well, I don't agree. And apparently neither did Nikon.

I have the K-5 and thus that is my reference.
With the K-5 a few hot pixels can appear if pushed really hard, but dark frames is not at all mandatory. The images are clean and the noise is evenly distributed. The few hot pixels that appear are automatically detected by Lightroom and removed.

These white dots is something else and appears in thousands, Lightroom does not detect them as they appear to hold valid data. Using dark frame subtraction while shooting cuts the effective light gathering time in half. That is not ok. It hasn't been necessary before, why should it be now?
08-06-2016, 10:13 AM - 1 Like   #11
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QuoteOriginally posted by beholder3 Quote
That is very normal behaviour and the very reason why for ages there has been the concept of dark frame subtraction and that is the case for special astro cameras as well.

http://starcircleacademy.com/2012/10/darkframes/
https://www.dpreview.com/forums/thread/3617190

If you want to do it properly you not only have your light frames in raw, but also bias, flat and darkframes - the latter are required per focal length, per ISO, per sensor temperature.

The lazy noob approach is to just switch on the in-camera dark frame subtraction called "long exposure noise reduction". This is automatically at the right focal lnegth, ISO and temperature.

No issue at all, other than lack of user knowledge.

Go to a astro forum and let them teach you, how to approach this.
I have to say, that I find this post disappointing, as you personally don't know me, or how much time I have spent working on this type of photography. I have put in the time and for star trail photography, this is an issue that your mention of a manual dark frame subtraction won't fix. But needless to say, your points merit a response as I disagree with them.

This issue has been found before years prior and I would have hoped that Pentax would have taken similar steps to address it, which it appears they did not. Depending on your workflow and end result it can become problematic.

Don't really consider myself a noob, but will take it as you will. And for sure it's not "lack of user knowledge" sorry you feel necessary to take that approach. You can go to all the astro forums you want, and this particular issue will not be fixed as it's an issue that is different than traditional noise. I would also ask if you have tired this yourself? I have thousands of exposures and hours of time in stacking with various cameras. Only wanted to point out that this same problem existed in a different brand which uses the same sensor, the other company fixed it.

If you want to go through all the process of taking a dark frame and trying to manually subtract it that is fine. Net, there are plenty of cameras out there, basically all from Canon, Nikon, etc that can take such a exposure without creation of a white dot, which by the way is not that easy to remove even with a true dark frame ( I have tried it) and the white dots don't clean up as well as traditional dark noise, which tend to show up in red, red, or blue dots, which a dark frame subtraction can remove.

I had hoped that the K1 would at least equal the long exposure quality from other cameras I have used, none of which require taking a dark frame and manually removing the noise. again this is mostly for traditional stuck pixels, which are both larger and brighter than the dots. With any modern digital DSLR, you should be able to take a up to a 2 hour long series of stacks, anywhere from 30 seconds to 2 minutes to 3 minutes each and not have the dots, yes you will have noise, but most of that can be removed during the stacking process later on, as the dots will stay in the same place throughout the entire stacking process. The problem comes in when you combine the images.

Working with a intervalometer, you will always have a faint gap between the exposures, and I only know of one tool that will remove these in post, and that is "star tracer". By design it will move the stacked image in a series of controlled blurs, which will combine the gaps into complete trails, and help to give faint trails a brighter look, however this process of movement also moves the dots into dotted trails throughout the image that with a 36MP image will show up. Net, the dots have to be out prior to this final step, and manual dark frame in my experience will not remove them.
The in camera noise reduction, which you seem to feel is also noob feature, works well and in fact more than likely works better than any manual dark frame process, but it defeats the stacking process due to the gaping it creates.

As I already pointed out, Capture One can remove most of this in a raw file, but if you capture in jpg, then it will work on the dots.

Paul C
08-06-2016, 10:23 AM   #12
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QuoteOriginally posted by CarlG Quote
That picture of Mt St Helens is taken a bit after midnight on June 26th, according to the Exif. Probably not very warm, but it shouldn´t be very cold.
Probably high 40s (F). Too bad the image is not OOC JPEG as claimed by DPReview, otherwise, the EXIF including temps and shot settings would be intact. (Is RAW conversion using Lightroom.)


Steve
08-06-2016, 10:59 AM   #13
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QuoteOriginally posted by Paul2660 Quote
This issue has been found
You claim this, but have not yet provided any meaningful proof of it being any "issue" at all.
Until we can inspect the raw file of the exact image you showed per screenshot there is not "issue", there just is a non-convincing claim.

QuoteOriginally posted by Paul2660 Quote
equal the long exposure quality from other cameras I have used, none of which require taking a dark frame and manually removing the noise.
If you read my post carefully, you'll find that I just said, dark frame subtraction is the key. For the easy approach you do not need to do it manually, even though I am under the impression most users serious about it do it. But it seems you have not even used the automatic DFS in camera, or am I wrong?

If there are unusual "white dots" I'd like to see them in a raw file when using DFS. Take a shot with DFS and share the raw if it shows "white dots".

QuoteOriginally posted by Paul2660 Quote
The in camera noise reduction, which you seem to feel is also noob feature, works well and in fact more than likely works better than any manual dark frame process, but it defeats the stacking process due to the gaping it creates.
That is more to the point. For your application you do not want to use the normal procedure for removing this type of noise. Fine. But then don't complain about it and call it funny names.

QuoteOriginally posted by Paul2660 Quote
if you capture in jpg, then it will work on the dots.
You do not want to use noise reduction. You do not want use raw. Fine again. But : Calling the result an "issue" is a pure user issue.

Generally you might want to read the following sentences:
QuoteQuote:
Although such “thermal” pixels are very common in digital camera sensors and are supposed to show up when shooting long exposures, camera manufacturers usually clean them up, whether you shoot in RAW or JPEG format. This clean up happens in the image processing pipeline, before RAW and JPEG files are generated.
https://photographylife.com/nikon-d810-thermal-noise-issue
So the "issue" at worst is that the Pentax K-1 is not pre-cooking the "raw"s as much as Canikon.
If you prefer pre-cooked raws, fine. Most users don't.
08-06-2016, 11:43 AM   #14
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@ Paul2660 Could you please check what the internal camera temperature was when dots first appear?
If the K-1 is anything like the K-5 the temperature is noted in the exif data and can be viewed with Exif viewer (At least I think it was called exif viewer, or maybe it was exif tool? I'm currently not at home and can't check the name right now).
08-06-2016, 12:39 PM   #15
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QuoteOriginally posted by beholder3 Quote
You claim this, but have not yet provided any meaningful proof of it being any "issue" at all.
Until we can inspect the raw file of the exact image you showed per screenshot there is not "issue", there just is a non-convincing claim.



If you read my post carefully, you'll find that I just said, dark frame subtraction is the key. For the easy approach you do not need to do it manually, even though I am under the impression most users serious about it do it. But it seems you have not even used the automatic DFS in camera, or am I wrong?

If there are unusual "white dots" I'd like to see them in a raw file when using DFS. Take a shot with DFS and share the raw if it shows "white dots".


That is more to the point. For your application you do not want to use the normal procedure for removing this type of noise. Fine. But then don't complain about it and call it funny names.



You do not want to use noise reduction. You do not want use raw. Fine again. But : Calling the result an "issue" is a pure user issue.

Generally you might want to read the following sentences:
https://photographylife.com/nikon-d810-thermal-noise-issue
So the "issue" at worst is that the Pentax K-1 is not pre-cooking the "raw"s as much as Canikon.
If you prefer pre-cooked raws, fine. Most users don't.

I love the time it takes to break out a post. You have more time than I do.

We can call it a disagreement.

Net take the camera out, shoot it for a series of long exposures, you will see white dots, how you choose to remove them I guess is up to you. Not using raw for this type of work to me is a mistake to others it may be fine.

I have posted examples from my camera K1 and my older D800e, which showed the exact same issue. Both are in a previous thread, did not want to repost. I would be happy to send you a raw file, showing the issue, send me an email and I will set it up in my dropbox. The problem, issue, whatever someone want to call it was a big enough issue that Nikon recalled the D810 to fix it. The same issue was fixed in the D800e on early cameras, I owned 2, one was clean the earlier was not. On the D800e the fix was not made public as on the D810. My D810 showed it immediately on the first shoot and within 2 weeks, Nikon had recalled all D810's for this issue, which I posted in a previous post with a link to the recall. If the issue/problem etc was not exactly the same as what was seen in both Nikon cameras using the same Sony 36MP chip, I would not have brought to this forum's attention as I felt there might be some photographers using the camera in the same method I am and thus they will see the same problem. I still call it a problem as it was totally fixed with firmware in the Nikon D810.

Not at all trying to slam Pentax as I feel the advantages of the K1 far out weight this type of shortfall.

Paul C

---------- Post added 08-06-16 at 12:40 PM ----------

QuoteOriginally posted by Gimbal Quote
@ Paul2660 Could you please check what the internal camera temperature was when dots first appear?
If the K-1 is anything like the K-5 the temperature is noted in the exif data and can be viewed with Exif viewer (At least I think it was called exif viewer, or maybe it was exif tool? I'm currently not at home and can't check the name right now).
Yes I will look at that tonight.

Paul C
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