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colourful dots on picture during long exposure D800, please help?

ckhuu

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ckhuu Registered since 25th Jul 2012
Wed 14-Nov-12 01:25 PM | edited Thu 15-Nov-12 04:16 PM by ckhuu

Dear All,
Sorry if this topic has been discussed before but i can't seem to find it. I had the D800 since July. I love the camera until recently, i had an opportunity to shoot long exposure night shots. I noticed any shots longer than 1 minute i would get colour artefacts like confetti on the picture?
I had turned the LENR on and it still persist. What am i doing wrong? I have tried to contact the local nikon site but the technical support is down or something that page won't open.

please find the attached sample pictures of different exposure time.
please note samples have been cropped to see the artefacts better.
83sec exposure, 14mm, ISO100, f/8

Click on image to view larger version


301sec, 14mm, iso 100, f/22
Click on image to view larger version


367sec exposure, same settings
Click on image to view larger version


481sec, 14mm, iso100, f/22
Click on image to view larger version


thanks for your advice!

Gromit44

UK
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#1. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 0

Gromit44 Registered since 04th Jan 2012
Wed 14-Nov-12 12:29 PM

The sample pictures aren't showing - it just says 'private image' on each one.

ckhuu

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#2. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 1

ckhuu Registered since 25th Jul 2012
Thu 15-Nov-12 12:30 AM

Ok the pictures can be seen now.

Gromit44

UK
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#3. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 2

Gromit44 Registered since 04th Jan 2012
Thu 15-Nov-12 12:14 PM

I'd have said they were a mixture of hot pixels and stuck pixels - http://photographylife.com/dead-vs-stuck-vs-hot-pixels - they appear to be completely random though, so I'm not sure.

Gromit44

UK
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#4. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 3

Gromit44 Registered since 04th Jan 2012
Thu 15-Nov-12 12:19 PM

PS. Are those pics JPEG or NEF?

wmarkle

King City ON, CA
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#5. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 4

wmarkle Silver Member Nikonian since 24th Feb 2009
Thu 15-Nov-12 01:22 PM

Since those "dots" are aligned on the lower horizon, I would assume they are lights along the distant shoreline.

ckhuu

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#6. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 5

ckhuu Registered since 25th Jul 2012
Thu 15-Nov-12 02:51 PM

Those pics were taken in raw format, i converted them to jpeg and cropped them to post here.

the dots are everywhere in the pictures and it can be seen on the camera screen.

I have heard of white spot hot pixels but i haven't been able to find an answer to coloured spots. thanks.

cbrandin

US
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#7. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 0

cbrandin Silver Member Nikonian since 28th Nov 2011
Thu 15-Nov-12 03:04 PM | edited Thu 15-Nov-12 03:05 PM by cbrandin

These are not hot pixels (mostly), rather it is a long exposure noise - which is a type of thermal noise, not stuck pixels. Colored spots are to be expected because in order to get white dots all three colors (RGB) would have to be noisy in equal amounts. Thermal noise affects pixel wells individually - that is, red green and blue pixels are affected separately.

The "long exposure" noise reduction feature can be used to mitigate this to a large extent. However, when you use long exposure NR images take twice as long to capture because there is the actual exposure and then an additional exposure taken with the shutter closed.

Visit my Nikonians gallery.

ckhuu

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#8. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 3

ckhuu Registered since 25th Jul 2012
Thu 15-Nov-12 03:09 PM

>I'd have said they were a mixture of hot pixels and stuck
>pixels -
>http://photographylife.com/dead-vs-stuck-vs-hot-pixels - they
>appear to be completely random though, so I'm not sure.
>

thank you so much for the link, it was helpful, it might be one of those, i will have to contact nikon to get a definitive diagnosis of the problem.
cheers

ckhuu

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#9. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 7

ckhuu Registered since 25th Jul 2012
Thu 15-Nov-12 03:15 PM

>These are not hot pixels (mostly), rather it is a long
>exposure noise - which is a type of thermal noise, not stuck
>pixels. Colored spots are to be expected because in order to
>get white dots all three colors (RGB) would have to be noisy
>in equal amounts. Thermal noise affects pixel wells
>individually - that is, red green and blue pixels are affected
>separately.
>
>The "long exposure" noise reduction feature can be
>used to mitigate this to a large extent. However, when you
>use long exposure NR images take twice as long to capture
>because there is the actual exposure and then an additional
>exposure taken with the shutter closed.

I see, does that mean everybody's D800/D800E have these noise?
I did turn on the Long exposure NR and the end results are the same.

I used both camera raw and LR 4 to import the pics but i guess it will not map them out or render them automatically.

Gromit44

UK
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#10. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 9

Gromit44 Registered since 04th Jan 2012
Fri 16-Nov-12 11:46 AM

I haven't seen that sort of noise (i.e. bright spots as opposed to general noise in shadow/underexposed areas) with my 800E - but then I haven't done any exposures longer than 30 seconds.

Although the spots in your pics appear completely random (indicating they're not stuck pixels) it might be an idea to repeat the exposures with the lens cap on just to make sure.

By the way - I just noticed the latest firmware update for the Nikon V1 and J1 cameras adds a pixel mapping option to the setup menu - I wonder why they haven't added this to the D800's firmware.

http://www.google.co.uk/url?sa=t&rct=j&q=pixel%20mapping%20firmware%20&source=web&cd=1&cad=rja&ved=0CDEQFjAA&url=http%3A%2F%2Fwww.nikonsupport.eu%2Feurope%2FFirmware%2FJ1%2FPixel%2FNikon1_FirmUp_En_01.pdf&ei=cD2mUIKPC-ml0QWagIGoAg&usg=AFQjCNHJLvkzsNdDoTOPEgvjvKRguUx8cA

aay

CA
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#11. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 9

aay Registered since 11th Jul 2010
Sun 18-Nov-12 12:40 AM

I've done some number of very long exposures and two of my friends who are into long exposure photographs have done many more. We all own D800 (not E, but I would not expect any difference in this regard). This is what you will get with D800. It is a temperature noise - the longer sensor is working the hotter it gets and it produces such noise. It is not that bad on less megapixel cameras.

At this time, based on all the reading I've done on the subject, I am forced to use Long Exposure NR which doubles the exposure time. This is unfortunate as it leads to fewer opportunities to take a shot you want. Also, I think the only way out of this (if you realize that your Long Exposure won't exposure the way you want) is to switch off the camera (and maybe even take the battery out) and then switch it back on.

If you do not use Long Exposure NR then you will have to deal with this noise in post production which will take a while since the noise produces spots of different color and size.

Alex
http://www.yermakov.net

FrankSRGB

US
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#12. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 11

FrankSRGB Registered since 09th Aug 2009
Sun 18-Nov-12 03:00 AM

Did you give the camera enough time to finish with the dark frame?

Most of your posted images have exposures over 6 minutes long. Which means you shouldn't shut the camera off for 12 minutes after the you first released the shutter. If you did shut it off before then, LENR would not have been performed.

aay

CA
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#13. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 12

aay Registered since 11th Jul 2010
Sun 18-Nov-12 06:20 AM | edited Sun 18-Nov-12 06:23 AM by aay

It is strange that OP had LENR turned on but still got that noise. In my experience that noise appear only with LENR turned off. But then again - with this camera I don't know whether to be surprised by any issue or not anymore.

Alex
http://www.yermakov.net

Gromit44

UK
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#14. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 12

Gromit44 Registered since 04th Jan 2012
Sun 18-Nov-12 12:46 PM

And the last shot is over 8 minutes so it would have been 16 minutes with LENR switched on.

FrankSRGB

US
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#15. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 14

FrankSRGB Registered since 09th Aug 2009
Sun 18-Nov-12 03:43 PM

aay,

Yeah, it is strange. My experience is the same as yours. It even looks like LENR wasn't turned on, which is why I questioned if the dark frame was actually taken.

I wouldn't be so hasty to blame the camera until operator error has been ruled out To know the camera has the LENR feature is one thing, to understand you have to wait (perhaps 16 minutes as Gromit44 pointed out) to turn the camera off is another.

RTFM is something we rarely do as a shoot is in progress, especially in the dark. If this was the 1st time the OP used the feature it's quite understandable how the camera could be shut off prematurely.


>At this time, based on all the reading I've done on the subject, I am forced
>to use Long Exposure NR which doubles the exposure time. This is unfortunate
>as it leads to fewer opportunities to take a shot you want.
>
>Also, I think the only way out of this (if you realize that your Long Exposure
>won't exposure the way you want) is to switch off the camera (and maybe even
>take the battery out) and then switch it back on.

You don't have to give up opportunities to take the shots you want. You can just turn off LENR and postpone taking the dark frame shot(s) until AFTER you've taken all your photographs. You can then subtract dark frames manually during post-processing instead of letting LENR do it in-camera. This is quite common in astrophotography circles. You can probably find much more info on the subject at Nikonians Astrophotography forum, but here's a couple links to give an idea......

http://darkclearskies.blogspot.com/2012/02/why-subtract-dark-frames.html
http://en.wikipedia.org/wiki/Dark-frame_subtraction


ckhuu,

Given the above, it may not be too late for you rescue your photos in post. I'd check with the folks in the Astrophotography forum to see what your chances of success are at taking a dark frame at this late date.

If you have Capture NX2, you might want to try the Astro NR feature in the Develop section. It's not the same as using LENR in-camera, but it's fast & easy and worth a try.

Regards,
Frank

kj_fi

Vantaa, FI
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#16. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 15

kj_fi Silver Member Nikonian since 18th Jul 2007
Sun 18-Nov-12 04:18 PM

Hi,

it seems to be perfectly on the shoreline. Random noise would be everywhere. Must be strong but pointed lights flashing randomly (car lights on the shore, buoys on the water, traffic lights, etc.).

In a long exposure they just become more apparent because normally, you wouldn't see them all the time. In a "blink of an eye" you might see only one or two lights but your camera's sensor collects them all during the 8 minute (or whatever) exposure.

Best regards,
Kari

briantilley

Paignton, UK
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#17. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 16

briantilley Gold Member Deep knowledge of bodies and lens; high level photography skills Donor Ribbon awarded for his support to the Fundraising Campaign 2014 Nikonian since 26th Jan 2003
Sun 18-Nov-12 05:01 PM

>it seems to be perfectly on the shoreline. Random noise would
>be everywhere.

Just to be clear, Cam is not talking about the row of lights on the shoreline, but the small bright or coloured pixel-size spots that appear randomly across the whole image, that can be seen on the larger gallery versions.

Brian
Welsh Nikonian

tooslo

UM
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#18. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 11

tooslo Silver Member Nikonian since 18th Jun 2012
Sun 18-Nov-12 07:35 PM


>
>At this time, based on all the reading I've done on the
>subject, I am forced to use Long Exposure NR which doubles the
>exposure time. This is unfortunate as it leads to fewer
>opportunities to take a shot you want. Also, I think the only
>way out of this (if you realize that your Long Exposure won't
>exposure the way you want) is to switch off the camera (and
>maybe even take the battery out) and then switch it back on.
>
>If you do not use Long Exposure NR then you will have to deal
>with this noise in post production which will take a while
>since the noise produces spots of different color and size.

I am curious. Have you tried using dark frame subtraction? Perhaps you'd only need a few dark frames per shoot.

I haven't had the occasion yet to try to perform the NR in post, but I would have imagined it would have been as simple as grabbing a dark frame at that start, middle and finish of a shot using a tool for this purpose. I would love to know if this technique would work as well as the built-in NR

ckhuu

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#19. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 18

ckhuu Registered since 25th Jul 2012
Mon 19-Nov-12 03:16 AM

>
>>
>>At this time, based on all the reading I've done on the
>>subject, I am forced to use Long Exposure NR which doubles
>the
>>exposure time. This is unfortunate as it leads to fewer
>>opportunities to take a shot you want. Also, I think the
>only
>>way out of this (if you realize that your Long Exposure
>won't
>>exposure the way you want) is to switch off the camera
>(and
>>maybe even take the battery out) and then switch it back
>on.
>>
>>If you do not use Long Exposure NR then you will have to
>deal
>>with this noise in post production which will take a
>while
>>since the noise produces spots of different color and
>size.
>
>I am curious. Have you tried using dark frame subtraction?
>Perhaps you'd only need a few dark frames per shoot.
>
>I haven't had the occasion yet to try to perform the NR in
>post, but I would have imagined it would have been as simple
>as grabbing a dark frame at that start, middle and finish of a
>shot using a tool for this purpose. I would love to know if
>this technique would work as well as the built-in NR

Dear All,
thanks for replying with all the possibilities. When i tried the first Long Exposure without LENR on, i turned it on right away thereafter. As for LENR completing the exposure, that i am not sure, i waited until the image appeared on the lcd, i assumed it was done. Possibly user error.
I finally was able to contact Nikon Asia with some of the my examples. they asked if i used any filters if not then send it in for service? I wish i could without spend a bomb on filters for the 14-24mm. lol... but no i didn't.
i am based in vietnam now and i bought the camera in singapore. In order to get a definitive diagnosis/fix on the matter, i will have to pay Nikon vietnam for the service fees which kinda sucks but no choice.
If it's inherent for a megapixel camera alike, then i will live with it and use post processing as above-mentioned.



ckhuu

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#20. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 15

ckhuu Registered since 25th Jul 2012
Mon 19-Nov-12 04:15 AM

>aay,
>
>Yeah, it is strange. My experience is the same as yours. It
>even looks like LENR wasn't turned on, which is why I
>questioned if the dark frame was actually taken.
>
>I wouldn't be so hasty to blame the camera until operator
>error has been ruled out To know the camera has the LENR
>feature is one thing, to understand you have to wait (perhaps
>16 minutes as Gromit44 pointed out) to turn the camera off is
>another.
>
>RTFM is something we rarely do as a shoot is in progress,
>especially in the dark. If this was the 1st time the OP used
>the feature it's quite understandable how the camera could be
>shut off prematurely.
>
>

>>At this time, based on all the reading I've done on the
>subject, I am forced
>>to use Long Exposure NR which doubles the exposure time.
>This is unfortunate
>>as it leads to fewer opportunities to take a shot you
>want.
>>
>>Also, I think the only way out of this (if you realize
>that your Long Exposure
>>won't exposure the way you want) is to switch off the
>camera (and maybe even
>>take the battery out) and then switch it back on.
>
>You don't have to give up opportunities to take the shots you
>want. You can just turn off LENR and postpone taking the dark
>frame shot(s) until AFTER you've taken all your photographs.
>You can then subtract dark frames manually during
>post-processing instead of letting LENR do it in-camera. This
>is quite common in astrophotography circles. You can probably
>find much more info on the subject at Nikonians
>Astrophotography forum, but here's a couple links to give an
>idea......
>
>http://darkclearskies.blogspot.com/2012/02/why-subtract-dark-frames.html
>http://en.wikipedia.org/wiki/Dark-frame_subtraction
>
>
>ckhuu,
>
>Given the above, it may not be too late for you rescue your
>photos in post. I'd check with the folks in the
>Astrophotography forum to see what your chances of success are
>at taking a dark frame at this late date.
>
>If you have Capture NX2, you might want to try the Astro NR
>feature in the Develop section. It's not the same as using
>LENR in-camera, but it's fast & easy and worth a try.
>
>Regards,
>Frank
thank you so much Frank, that's enlightening as it is the first i am using this LENR feature and
may not be doing it right.

briantilley

Paignton, UK
30235 posts

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#21. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 19

briantilley Gold Member Deep knowledge of bodies and lens; high level photography skills Donor Ribbon awarded for his support to the Fundraising Campaign 2014 Nikonian since 26th Jan 2003
Mon 19-Nov-12 07:30 AM

To be honest, I'm not sure if the image appears before or after the dark frame is completed - but either way it's easy to tell because "job--nr" flashes in the top display whilst the dark frame is being created. The camera must not be turned off while that is displayed.

Brian
Welsh Nikonian

ckhuu

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#22. "RE: colourful dots on picture during long exposure D800, please help?" | In response to Reply # 21

ckhuu Registered since 25th Jul 2012
Mon 19-Nov-12 10:07 AM

>To be honest, I'm not sure if the image appears before or
>after the dark frame is completed - but either way it's easy
>to tell because "job--nr" flashes in the top
>display whilst the dark frame is being created. The camera
>must not be turned off while that is displayed.

Thanks Brian for the input, so i did turned on the NR but you guys are right, i probably didn't wait until the JOB NR finished. I just did some shots with the lens cap on and noticed the JOB NR. I guess during the shoot, i was using a remote and sitting indoors, once the timer was up, i ran out and checked the pics in the dark. I will go out for a real test when time permits.
I am glad i turned to nikonian forum for help! cheers.

G