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Subject: "I need help. ND400 long exposure" Previous topic | Next topic
TakeTwo Silver Member Nikonian since 26th Jul 2009Fri 29-Apr-11 05:18 AM
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"I need help. ND400 long exposure"


South Lake Tahoe, US
          

Hello group. I have a question for all of you and am hoping someone can help to explain my problem. I took several pictures today using my new nd400 filter so I could start capturing some daytime long exposure of the lake. In the posted image below I took with a 15 second exposure by stacking a nd-400 and nd8 (12stops total)filters. My problem is I had over 400 hundred hot or white pixels as I would say. I did not use any noise reduction. Am I asking to much for the camera's sensor.

Its seems to me that all those that say putting a lens cap on your lens and take pictures to find hot or dead pixels may want reconsider that. Is taking a picture with a 12 stop filter in some way making the camera's sensor work harder for light.

I'm at a loss here. I have never had any issues with my sensor? I think noise reduction on is a must. Has anyone shot a similar technique while using noise reduction and had or not had hot pixels.


d7k
12-24mm
exp. 15"
ISO 100
f:22
I cloned out the hot pixels in this image.


This is a 100% crop of the sky of a different image. No post work.

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Attachment #1, (jpg file)
Attachment #2, (jpg file)

  

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Replies to this topic
Subject Author Message Date ID
Reply message RE: I need help. ND400 long exposure
chris_platt Silver Member
29th Apr 2011
1
Reply message RE: I need help. ND400 long exposure
ericbowles Moderator
29th Apr 2011
2
Reply message RE: I need help. ND400 long exposure
TakeTwo Silver Member
29th Apr 2011
3
     Reply message RE: I need help. ND400 long exposure
ericbowles Moderator
29th Apr 2011
4
          Reply message RE: I need help. ND400 long exposure
TakeTwo Silver Member
29th Apr 2011
5
          Reply message RE: I need help. ND400 long exposure
ericbowles Moderator
29th Apr 2011
6
               Reply message RE: I need help. ND400 long exposure
TakeTwo Silver Member
30th Apr 2011
9
                    Reply message RE: I need help. ND400 long exposure
elec164 Silver Member
30th Apr 2011
10
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chris_platt Silver Member
30th Apr 2011
11
          Reply message RE: I need help. ND400 long exposure
chris_platt Silver Member
29th Apr 2011
7
               Reply message RE: I need help. ND400 long exposure
ericbowles Moderator
29th Apr 2011
8
                    Reply message RE: I need help. ND400 long exposure
TakeTwo Silver Member
01st May 2011
12
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TakeTwo Silver Member
01st May 2011
13
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KnightPhoto Gold Member
02nd May 2011
14
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TakeTwo Silver Member
02nd May 2011
15
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KnightPhoto Gold Member
03rd May 2011
16
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jmiguez Silver Member
03rd May 2011
17
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TakeTwo Silver Member
05th May 2011
19
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TakeTwo Silver Member
05th May 2011
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chris_platt Silver Member Nikonian since 04th Apr 2009Fri 29-Apr-11 11:41 AM
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#1. "RE: I need help. ND400 long exposure"
In response to Reply # 0


Newburg, US
          

Hot pixels can be expected with long exposures - anything over 1 second with the D7000. Did you have Long Exposure Noise Reduction (Long Exp. NR) turned on in the shooting menu? That feature is intended to correct this problem. Also, you should apply firmware update 1.02 if you haven't done so. The update addresses several important issues including changing the application of Long Exp. NR to any exposure over 1s if it is turned on (it used to be applied only to exposures over 8 seconds).

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ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Nikonian since 25th Nov 2005Fri 29-Apr-11 12:34 PM
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#2. "RE: I need help. ND400 long exposure"
In response to Reply # 1


Atlanta, US
          

The need for Long Exposure Nolise reduction starts with exposures of around 8 seconds. Essentially the camera takes a second image and looks at the difference between the two to identify and remove noise. It shoudl be effective on the hot pixels in your image. If not, you can contact Nikon to have hot pixels removed via software.

You'll notice that long exposure noise reduction causes the time between the shutter open and close to nearly double. This can be a little distracting and will cause you to be much more careful before pressing the shutter release as a 30 second exposure can take a minute or more by the time it is written to the card.

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TakeTwo Silver Member Nikonian since 26th Jul 2009Fri 29-Apr-11 01:34 PM
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#3. "RE: I need help. ND400 long exposure"
In response to Reply # 1


South Lake Tahoe, US
          

So 1 second is all it takes. In several of images that I took I notices during the same exposure length that not the same pixels were hot. To have them mapped would be difficult it would seem. I have taken many many pictures of exposure lengths at 1.6" to 2" with my copy of the d7k and not seen any pixels issues. I'll will be out in the field today and will run some exposures with the long noise reduction on. I'm really glad I ran theses shots yesterday as I'm traveling to Ireland in a few weeks and will be shooting many long exposures. I don't want to spend hours in post cloning them out. Thank you for your suggestions. Don

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ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Nikonian since 25th Nov 2005Fri 29-Apr-11 01:49 PM
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#4. "RE: I need help. ND400 long exposure"
In response to Reply # 3


Atlanta, US
          

<So 1 second is all it takes.>

No - that is not necessarily correct unless there is something else going on to cause noise.

Hot pixels are not exactly the same as noise but may be resolved in a similar mannar. Long exposure noise typically shows up at really long exposures - 1-2 seconds should not have a problem. 8-15 seconds and longer will be more likely to have issues. You don't need long exposure noise reduction at a 1-2 second exposure - but for long exposures like the image posted, you probably want it turned on.

And be sure your firmware is current as in the D7000 is does resolve some hot pixel issues.

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TakeTwo Silver Member Nikonian since 26th Jul 2009Fri 29-Apr-11 01:57 PM
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#5. "RE: I need help. ND400 long exposure"
In response to Reply # 4


South Lake Tahoe, US
          

Eric, I will address the firmware update today. Thanks for the comments. Several of the images I took yesterday I shot in bracket so I could do a HDR and I wanted the long and soft look on the waves and on the clouds. It seems to me that I am going to have a problem with gaps if I use the exposure on feature. Of I can shoot like I did and remove by clone tool in post. Is there a faster way in post work to remove the hot pixels. I use nx2. Don

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ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Nikonian since 25th Nov 2005Fri 29-Apr-11 02:12 PM
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#6. "RE: I need help. ND400 long exposure"
In response to Reply # 5
Fri 29-Apr-11 02:30 PM by ericbowles

Atlanta, US
          

One strategy to give the appearance of a long exposure is to use multiple exposures. You can create gauzy water or star trails by using the multiple exposure function. Each individual shutter release is using the camera setting of choice, but when they are combined into one image you get something similar to a long exposure.

Try a series of 10 exposures at a half second each.

For details see page 152 of the manual.

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TakeTwo Silver Member Nikonian since 26th Jul 2009Sat 30-Apr-11 01:27 AM
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#9. "RE: I need help. ND400 long exposure"
In response to Reply # 6


South Lake Tahoe, US
          

Eric, Yes I have shot many images by multiple exposure. But there really is no way to capture the images I want to get by using the multiple exposure method. nd filters and long exposure is all I know how to do to smooth out heavy seas crashing onto the beach. Tomorrow I spend time in the field again and will use the noise reduction in camera. I'm sure that is the problem that I am having.

Even star trails require a long exposure, and even longer if you put in DOF if you want to close focus on a subject.

I guess the only real way to get around this noise problem on the digital sensor is to shoot film.

How come my hot pixels are more red when shooting star trails at night, yet they are white crosses ( pixel peeping ) during the daytime shot that I posted up? Don

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elec164 Silver Member Nikonian since 15th Jan 2009Sat 30-Apr-11 01:10 PM
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#10. "RE: I need help. ND400 long exposure"
In response to Reply # 9


US
          

>How come my hot pixels are more red when shooting star trails
>at night, yet they are white crosses (pixel peeping) during
>the daytime shot that I posted up?

Since no one had given an opinion on why they are white in this instance, and red, green or blue in your star trails, I’ll give it a try. The subject can get quite complex and my understanding is rudimentary so take my logical conclusion with a grain of salt.

There are a number of sources of noise in digital imaging, but I believe the main one in this instance is leakage current (or I believe it is also referred to as dark current) and possibly shot noise (or possible more appropriately called dark shot noise). In long exposure imaging the thermal affect will increase the amount of leakage current. And being a Bayer sensor array, depending on where the sensel falls in the array, it will provide signal information for either the red, green or blue spectrum. Also being a Bayer array the final value for a pixel in that location in the image array is determined by averaging out and adding in the values of adjacent sensels. So in your low light image (star trails) the leakage current would cause a high signal in a sensel. But the signal in the surrounding sensels will be low, so the filter the high leakage signal falls under will dominate and cause the hot pixel to be that color (red, green or blue). But in your bright light long exposure image the surrounding sensel will also have a higher signal (but not as high as the dark shot noise sensel) so when they are averaged out and added in with the hot sensel the result would appear brighter, or more white’ish then the surrounding pixels.

Being that this noise is relatively a constant, it can be dealt with utilizing a dark frame subtraction; either using the in-camera long exposure NR or later in a PP editor such as Photoshop by taking and utilizing a dark frame capture of equal exposure time. The latter would save you time in the field in that one dark frame capture could be used on multiple image captures, but would take more time in PP.

If someone more knowledgeable then myself finds fault in my logic, I would appreciate the corrections.

Pete

Pete

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chris_platt Silver Member Nikonian since 04th Apr 2009Sat 30-Apr-11 01:15 PM
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#11. "RE: I need help. ND400 long exposure"
In response to Reply # 9
Sat 30-Apr-11 11:18 PM by chris_platt

Newburg, US
          

"How come my hot pixels are more red when shooting star trails at night, yet they are white crosses ( pixel peeping ) during the daytime shot that I posted up?"

I posted a reply here with essentially the same explanation as above, but made it to the finish line a little later. So instead of being repetitive, I thought I'd just post this great link.

EDIT oops, posted the wrong link. This is the one I meant to post. http://webpages.charter.net/bbiggers/DCExperiments/html/hot_pixels.html

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chris_platt Silver Member Nikonian since 04th Apr 2009Fri 29-Apr-11 03:14 PM
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#7. "RE: I need help. ND400 long exposure"
In response to Reply # 4


Newburg, US
          

"<So 1 second is all it takes.>

No - that is not necessarily correct unless there is something else going on to cause noise."

Eric, apparently in the D7000 it may only take exposures longer than 1 second to start getting hot pixels. In the firmware update released on April 25th (1.02) Nikon changed the application of long exposure noise reduction from 8 secs. down to 1 sec.

From Nikon's firmware update page: Noise reduction processing is now performed with shutter speeds slower than 1 s (previously 8 s) when On is selected for Long Exp. NR in order to reduce the bright spots that occur with shooting of still images at slow shutter speeds.

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ericbowles Moderator Awarded for his in-depth knowledge and high level skills in various areas, especially Landscape and Wildlife Photoghraphy Writer Ribbon awarded for for his article contributions to the community Nikonian since 25th Nov 2005Fri 29-Apr-11 03:24 PM
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#8. "RE: I need help. ND400 long exposure"
In response to Reply # 7


Atlanta, US
          

Chris - thanks for clarifying. I hadn't noticed that message. That's an important change.


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TakeTwo Silver Member Nikonian since 26th Jul 2009Sun 01-May-11 01:59 PM
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#12. "RE: I need help. ND400 long exposure"
In response to Reply # 8


South Lake Tahoe, US
          

So thank you all for your input and suggestions. I went out yesterday after spending a few hours clean two sensors and several filters. And in fact with the noise reduction on all my long exposures came out perfect. It will be a great thing when we will not need to use a noise reduction setting at all. Wishful thinking?
I hope not. Don

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TakeTwo Silver Member Nikonian since 26th Jul 2009Sun 01-May-11 10:25 PM
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#13. "RE: I need help. ND400 long exposure"
In response to Reply # 12


South Lake Tahoe, US
          

I wanted to mention one more thing that I did not realize. While shooting brackets with long noise reduction on, the camera lets you shoot all three shots before applying the noise reduction to the images. So if I have a total of 60 seconds of exposure for the 3 combined images, the camera will pause after the bracket capture and write in the noise reduction for 60 seconds. This is a good thing. Don

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KnightPhoto Gold Member Nikonian since 18th Dec 2006Mon 02-May-11 02:48 AM
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#14. "RE: I need help. ND400 long exposure"
In response to Reply # 13


Alberta, CA
          

Thanks for the info Don and guys. And if I might say so, very interesting daytime photo technique.

Do you focus prior to attaching the ND filters?

Best regards, SteveK

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TakeTwo Silver Member Nikonian since 26th Jul 2009Mon 02-May-11 04:22 AM
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#15. "RE: I need help. ND400 long exposure"
In response to Reply # 14


South Lake Tahoe, US
          

SteveK, I use the dial on the lens and focus to my hyper focal mark. I focus out to 4ft at f22 and out to 10 feet at f11 I want focus out to infinity but I care more about the foreground. So because I know my settings I don't have to take the ndx400 off the lens anymore for these kind of shots.

I shoot in manual but I set my aperture dial to f4 for my 12-24 lens that I use and then I can click on the live view and see pretty well for composition but not focus. I can then switch the dial to manual for my exposure settings. Don

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KnightPhoto Gold Member Nikonian since 18th Dec 2006Tue 03-May-11 02:07 AM
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#16. "RE: I need help. ND400 long exposure"
In response to Reply # 15


Alberta, CA
          

Thanks Don, very interesting!

Best regards, SteveK

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jmiguez Silver Member Nikonian since 17th Oct 2010Tue 03-May-11 02:28 AM
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#17. "RE: I need help. ND400 long exposure"
In response to Reply # 15


Lafayette, US
          

I really like the picture Don. It has such such an other world feeling. It is quite beautiful in its own way.

John

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TakeTwo Silver Member Nikonian since 26th Jul 2009Thu 05-May-11 01:48 AM
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#19. "RE: I need help. ND400 long exposure"
In response to Reply # 17


South Lake Tahoe, US
          

John, Thank your for your comment on my image. Yes It is different for sure. The winds were blowing 40 mph during my shot and the long exposure laid the waves down to nothing. The images came out smoother than what I wanted to achieve. Next time I will go 3 or 4 seconds. I already know what 1.5 seconds looks like. Don

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TakeTwo Silver Member Nikonian since 26th Jul 2009Thu 05-May-11 01:45 AM
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#18. "RE: I need help. ND400 long exposure"
In response to Reply # 13


South Lake Tahoe, US
          

>I wanted to mention one more thing that I did not realize.
>While shooting brackets with long noise reduction on, the
>camera lets you shoot all three shots before applying the
>noise reduction to the images. So if I have a total of 60
>seconds of exposure for the 3 combined images, the camera will
> pause after the bracket capture and write in the noise
>reduction for 60 seconds. This is a good thing. Don


Sorry folks, I made an incorrect comment about the the noise reduction allowing the bracket shots to finish before it shoots the blank image. I was using my user setting for focus and did not put it to manual mode where I use noise reduction. So the correct statement should be that after each shot the noise reduction does write a black image after each shot. Sorry for my confusion and leading some to the wrong conclusion. Don

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