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DPChallenge Forums >> Tips, Tricks, and Q&A >> Nikon nr reduction?
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12/14/2007 02:24:18 PM · #1
I have a nikon d50 and was wondering if the in camera noise reduction was worth using or not it makes the process time between shots really long when doin long exsposures.....worth using ? better way with program and what program ??
12/14/2007 02:27:25 PM · #2
Pesonally, I shoot almost exclusively in RAW. This way I have much more control over post processing - control of exposure, control of white balance, and control of all post processing including NR and sharpening, etc.

I personally use Noise Ninja for NR but many rave about Neat Image...
12/14/2007 02:30:45 PM · #3
This is essentially the same process as Dark Frame Subtraction. If you take a 1 minute exposure, the camera will then take a second 1 minute exposure with the 'lens cap on'. It then subtracts one from the other, thus removing a lot of the noise and hot pixels.

If you turn off long exposure NR, then you can do it manually using something like layers in Photoshop (I believe registax also offers dark frame subtraction). But you'll still have to shoot the dark frame yourself. Alternatively, if you don't want to use the Dark Frame method at all you can clone out hot pixels in PS, and use something like Noise Ninja for noise reduction.

Turning off NR is useful in situations where you are taking a sequence of long exposures. Just take the sequence, and then take the dark frame at the end if you want to, rather than using in-camera NR and having to wait for the automatic dark frame shot between exposures.
12/14/2007 02:32:36 PM · #4
I have used noise reduction feature in my Nikon D100 for really long exposure shots. For example, if I expose a photo for 75 seconds (night time photography), my image is literally unusable because it is full of white specks (very very grainy). Noise reduction, when enabled on my Nikon D100 takes the same amount of time to process as the photo was exposed. For example, 75 seconds of exposure takes 75 seconds or so to process NR before the image is recorded to the card so I can view it.

It does take some of the sharpness away from the image - ie, image looks quite smooth, but not very sharp. NR in camera is not to be used if you want to capture many images quickly, but it is a cool tool to use when you want to capture some neat looking night photos.
12/14/2007 02:33:55 PM · #5
Originally posted by jhonan:

This is essentially the same process as Dark Frame Subtraction. If you take a 1 minute exposure, the camera will then take a second 1 minute exposure with the 'lens cap on'. It then subtracts one from the other, thus removing a lot of the noise and hot pixels.

If you turn off long exposure NR, then you can do it manually using something like layers in Photoshop (I believe registax also offers dark frame subtraction). But you'll still have to shoot the dark frame yourself. Alternatively, if you don't want to use the Dark Frame method at all you can clone out hot pixels in PS, and use something like Noise Ninja for noise reduction.

Turning off NR is useful in situations where you are taking a sequence of long exposures. Just take the sequence, and then take the dark frame at the end if you want to, rather than using in-camera NR and having to wait for the automatic dark frame shot between exposures.


Oh! Is that how it works! Didn't know that......
12/14/2007 03:03:08 PM · #6
thanks for the input people
12/14/2007 03:05:13 PM · #7
Originally posted by mcrael:

Originally posted by jhonan:


Turning off NR is useful in situations where you are taking a sequence of long exposures. Just take the sequence, and then take the dark frame at the end if you want to, rather than using in-camera NR and having to wait for the automatic dark frame shot between exposures.


Oh! Is that how it works! Didn't know that......


Yup, that's how it works. Why does the dark exposure need to be the same length as the true exposure? Because sensor noise increases dramatically with increased exposure times. There is heat buildup in the sensor, and there are "hot zones" in the camera (they vary by make and by model) that make certain areas of the sensor get hotter than other areas.

For this reason, jhonan's suggestion (a single dark frame to be used for all the exposures) is of limited utility. It's better than nothing, if you need to have the functionality of shooting a whole bunch of long exposures back-to-back in as short a time as possible, but it will not be optimized for any of the frames except the one it matches in exposure length.

R.
12/14/2007 06:14:20 PM · #8
Originally posted by Bear_Music:

For this reason, jhonan's suggestion (a single dark frame to be used for all the exposures) is of limited utility. It's better than nothing, if you need to have the functionality of shooting a whole bunch of long exposures back-to-back in as short a time as possible, but it will not be optimized for any of the frames except the one it matches in exposure length

Yes, I was giving this option as a 'last resort' - The other night I was shooting multiple astrophotography shots of 1 minute exposure for stacking, and couldn't afford to wait for the 1 minute between shots. I took a 1 minute dark frame at the end instead.
12/14/2007 07:53:09 PM · #9
Originally posted by jhonan:

The other night I was shooting multiple astrophotography shots of 1 minute exposure for stacking, and couldn't afford to wait for the 1 minute between shots. I took a 1 minute dark frame at the end instead.


As long as they are all 1-minute exposures, and the last, dark frame is 1 minute, that should work pretty well. It's when the intervening exposures are of different lengths that things become problematic.

R.
12/14/2007 09:21:30 PM · #10
Originally posted by Bear_Music:

Originally posted by jhonan:

The other night I was shooting multiple astrophotography shots of 1 minute exposure for stacking, and couldn't afford to wait for the 1 minute between shots. I took a 1 minute dark frame at the end instead.


As long as they are all 1-minute exposures, and the last, dark frame is 1 minute, that should work pretty well. It's when the intervening exposures are of different lengths that things become problematic.

R.


Yup! And if you have the time after the "light frames," then shoot multiple dark frames and average them. That will eliminate random noise from the dark frames and further improve your results.
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