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Subject: "d40x - Time Lapse problem - Pinkish Corners in Night Sk..." Previous topic | Next topic
austinpm1 Registered since 05th Oct 2006Wed 02-Apr-08 04:27 AM
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"d40x - Time Lapse problem - Pinkish Corners in Night Sky"



          

I've been experimenting a lot with time-lapse photography of night sky and star trails but one problem that keeps coming up is the top left and right corners of my shots get a pinkish purple glow no matter what i'm shooting. the longer the shot (30 minute max for my d40x) the brighter the corner glows. any idea what this could be?

i've even tried covering the camera body with a black baseball hat while the exposure is happening in case its a light leak from the rear or the lens or something...

thanks for any insights.

Pat

  

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Subject Author Message Date ID
Reply message RE: d40x - Time Lapse problem - Pinkish Corners in Nigh...
blw Moderator
02nd Apr 2008
1
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austinpm1
02nd Apr 2008
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DeanAZ Moderator
02nd Apr 2008
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austinpm1
02nd Apr 2008
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DeanAZ Moderator
02nd Apr 2008
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blw Moderator
03rd Apr 2008
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blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004Wed 02-Apr-08 08:28 AM
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#1. "RE: d40x - Time Lapse problem - Pinkish Corners in Night Sky"
In response to Reply # 0


Richmond, US
          

That glow comes from thermal radiation from your camera's electronics, and as you note is dependent on how long the electronics are active - which is why longer exposures make it worse.

There is an option somewhere in your menus for Long Exposure Noise Reduction - turn it on and this will go away. However, be aware that it works by taking another dark exposure and subtracting that from the real exposure, which means that you take twice as long to make each image.

_____
Brian... a bicoastal Nikonian and Team Member

My gallery is online. Comments and critique welcomed any time!

  

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austinpm1 Registered since 05th Oct 2006Wed 02-Apr-08 12:05 PM
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#2. "RE: d40x - Time Lapse problem - Pinkish Corners in Night Sky"
In response to Reply # 1



          

so then i can't composite two (or more) 30 minute exposures since its going to take 30 minutes between each shot this way, right?

I've been trying to make several hour star trail shots showing a near circular path - unachievable if i've got a 30 minute gap between shots...

  

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DeanAZ Moderator Expert nature photographer Nikonian since 28th Apr 2007Wed 02-Apr-08 04:20 PM
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#3. "RE: d40x - Time Lapse problem - Pinkish Corners in Night Sky"
In response to Reply # 2


Phoenix, US
          

You are correct the composited shots w/NR on will give gaps. If you intend to composite, try more shorter exposures. I have also used Capture NX color control points to get rid of the purple amp noise. Since the sky is usually black where the noise is located (top left & right) and always in the same place, you can save the step and apply it to all your night long exposure shots. Unfortunately the D40 does not control the amp noise well a result of the small body size I imagine. Hope this helps.

Dean
Phoenix, Arizona USA
Nikonians Team Member
Website: The Splendid Silence of Light

Recent Trips: Grand Canyon 2012 Glen Canyon 2012 West Clear Creek

Visit my Nikonians gallery.

  

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austinpm1 Registered since 05th Oct 2006Wed 02-Apr-08 09:24 PM
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#4. "RE: d40x - Time Lapse problem - Pinkish Corners in Night Sky"
In response to Reply # 3



          

good point about more/shorter exposures but won't the NR take take in between time that is proportionate to the exposure? i guess a 1 minute shot + 1 minute NR gap is better than 25 minute exposure + 25 minute NR gap, right?

great pix in you gallery btw. I was just at Bryce and Zion in Utah last week. two of THEE most beautiful places I've ever been. Took quite a few shots there myself...

  

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DeanAZ Moderator Expert nature photographer Nikonian since 28th Apr 2007Wed 02-Apr-08 10:18 PM
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#5. "RE: d40x - Time Lapse problem - Pinkish Corners in Night Sky"
In response to Reply # 4


Phoenix, US
          

I guess I was not clear that the multiple shorter exposures would have NR off. I think you get a better signal to noise ratio with shorter exposures and the amp noise would not be as noticeable. I don't have much experience with composites but I know some have had good success.

Dean
Phoenix, Arizona USA
Nikonians Team Member
Website: The Splendid Silence of Light

Recent Trips: Grand Canyon 2012 Glen Canyon 2012 West Clear Creek

Visit my Nikonians gallery.

  

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blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004Thu 03-Apr-08 07:45 AM
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#6. "RE: d40x - Time Lapse problem - Pinkish Corners in Night Sky"
In response to Reply # 2


Richmond, US
          

No DSLR I know of controls amp noise well.

However, in night shots, it is relatively straightforward to edit it away in postprocessing. In Photoshop, just do Select->Color Range and click on the pink. Select->Feather the selection. Then Layer->New Adjustment->Hue/Saturation. Pick the black color that matches the background and tick the Colorize box.

_____
Brian... a bicoastal Nikonian and Team Member

My gallery is online. Comments and critique welcomed any time!

  

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Forums Lobby GET TO KNOW YOUR CAMERA & MASTER IT Nikon D60/D50/D40 (Public) topic #27226 Previous topic | Next topic


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