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Long exposures are noisy



 
 
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  #1  
Old August 1st 07, 09:16 AM posted to rec.photo.digital.slr-systems
D.M. Procida
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Posts: 104
Default Long exposures are noisy

The pictures themselves are great - but the camera (Pentax K100D) makes
an absolute racket.

There's a bit of noise during the exposure itself, but afterwards, while
I presume the camera is processing it, it sings and coughs to itself at
length. Is this normal?

Also, it seems to take the camera as long to process a 30-second
exposure as it does to take the picture itself (i.e. before the camera
is ready for further action). Why should this be the case?

Daniele
  #3  
Old August 1st 07, 04:56 PM posted to rec.photo.digital.slr-systems
Marc Sabatella
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Posts: 228
Default Long exposures are noisy

Also, it seems to take the camera as long to process a 30-second
exposure as it does to take the picture itself (i.e. before the camera
is ready for further action). Why should this be the case?


This is the noise reduction feature (image noise, not audible noise)
that kicks in for long exposures. You can turn it off if you like,
either via the setup or custom menu.

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  #4  
Old August 2nd 07, 01:26 AM posted to rec.photo.digital.slr-systems
DoN. Nichols
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Posts: 405
Default Long exposures are noisy

According to D.M. Procida :
The pictures themselves are great - but the camera (Pentax K100D) makes
an absolute racket.

There's a bit of noise during the exposure itself, but afterwards, while
I presume the camera is processing it, it sings and coughs to itself at
length. Is this normal?

Also, it seems to take the camera as long to process a 30-second
exposure as it does to take the picture itself (i.e. before the camera
is ready for further action). Why should this be the case?


Well ... based on the Nikon D70, the default mode for long
exposures is "Long exp. NR" mode, which takes a second "non" picture with the same
exposure time as the actual exposure, but with the shutter closed. This
gives the camera a reference for the noise patterns for that length of
exposure at the temperature at which the camera is being used. This is
then subtracted digitally from the actual image, making for a much
better image than if you turn the NR mode off (which I do when shooting
fireworks, since I am more willing to live with the noise than to lose
the ability to take another shot right away.

Your camera may also offer a way to turn off the NR mode
(whatever they call it), and you should experiment with shooting two
long-exposure shots (one with and one without) just to show you what the
difference in appearance is, so you can know when you can live with the
noise as a tradeoff for the ability to shoot another exposure soon after
the first.

Enjoy,
DoN.
--
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  #5  
Old August 2nd 07, 01:36 AM posted to rec.photo.digital.slr-systems
Ray Macey
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Posts: 73
Default Long exposures are noisy

On Aug 2, 1:56 am, "Marc Sabatella" wrote:

This is the noise reduction feature (image noise, not audible noise)
that kicks in for long exposures. You can turn it off if you like,
either via the setup or custom menu.


It's more hot pixel reduction than noise reduction...

Ray

  #6  
Old August 3rd 07, 11:25 AM posted to rec.photo.digital.slr-systems
Pete D[_2_]
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Posts: 347
Default Long exposures are noisy


"DoN. Nichols" wrote in message
...
According to D.M. Procida :
The pictures themselves are great - but the camera (Pentax K100D) makes
an absolute racket.

There's a bit of noise during the exposure itself, but afterwards, while
I presume the camera is processing it, it sings and coughs to itself at
length. Is this normal?

Also, it seems to take the camera as long to process a 30-second
exposure as it does to take the picture itself (i.e. before the camera
is ready for further action). Why should this be the case?


Well ... based on the Nikon D70, the default mode for long
exposures is "Long exp. NR" mode, which takes a second "non" picture with
the same
exposure time as the actual exposure, but with the shutter closed. This
gives the camera a reference for the noise patterns for that length of
exposure at the temperature at which the camera is being used. This is
then subtracted digitally from the actual image, making for a much
better image than if you turn the NR mode off (which I do when shooting
fireworks, since I am more willing to live with the noise than to lose
the ability to take another shot right away.

Your camera may also offer a way to turn off the NR mode
(whatever they call it), and you should experiment with shooting two
long-exposure shots (one with and one without) just to show you what the
difference in appearance is, so you can know when you can live with the
noise as a tradeoff for the ability to shoot another exposure soon after
the first.


And is called dark frame subtraction.


 




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