Question about mandatory noise reduction in Nikon DSLRs

[DQE]

I just came across this info in a subscription-based camera and lens review site that I subscribe to and thought it might be worth some discussion:

"Nikon’s latest DSLRs (D3x, D3, etc) are apparently not suitable for astrophotography because the RAW file has been pre-processed by the camera to remove “noise” eg faint stars!"

"In normal photos that would never be an issue, because such detail could never be distinguished from noise. But when special processing is applied across multiple exposures to eliminate the random noise, real detail that was below the noise threshold of a single frame can be revealed—a faint star. For astrophotographers, the type of noise processing is therefore a critical concern."

http://diglloyd.com/prem/prot/DAP/Noise4/Overview.html

(I think this page is behind a subscription paywall but I am not 100% sure.)
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With the advent of the Nikon 800E camera body, I have begun to wonder if switching to Nikon from Canon would be desirable. Yet the above assertion is a concern since I occasionally do make long (> 30 sec) exposures and I would like to have the option to make long-exposure, star-filled night sky photographs. Although I mostly shoot macro, I don't want to be limited with respect to other specialty photographic explorations.

Can anyone comment as to the truth and relevance of the above information? AFAIK, it's not relevant to most macro photography. I would like to have the option to turn off *all* of the in-camera noise reduction, and instead use one's preferred algorithms and software packages. I realize that all manufacturers do some mandatory image processing of their raw images but the above processing is distressing to me as a fixed requirement.

[Babylonia]

Yes, subscription for the Lloyd Chambers wep-page is behind a paywall.

As for several Nikon camera's some "settings" within the camera are used to reduce noise. Even if you switch off the settings in the camera under certain circumstances there is still some noise reduction. Maybe that is what Lloyd Chambers is referring to (I have no access to his paid web-pages).
But that is true only as a "tag" included in a RAW file for the noise reduction setting, and that this default noise reduction works out directly to JPG files, as output from the camera. This default noise reduction only is used by high ISO values. Below a certain ISO value (1600 - 3200 ?? dependent from camera model), there is no default noise reduction. The camera manuals are referring to this.

As for RAW files, these noise reduction settings "as a tag" are copied by the own Nikon RAW-converter into "Capture NX2". If you leave it (don't touch the setting within the software), also within the software some noise reduction is done comparing to the default noise reduction at JPG-files (only as a default above a certain high ISO value). But within the RAW-converter itself, you can switch off the setting. So at least for RAW files there can be made a difference in comparison to the in-camera JPG-files.

Many included camera settings are copied by Capture NX2 into the RAW-processing, but every setting can be switched off within the software. Adobe Camera RAW not all settings are copied but software make use of their own default values. Also these settings can be switched off.

Several RAW converters have different routines to de-mosaic the RAW Bayer pattern RGGB data. So switching off noise reduction in Capture NX2 do have another output than switching off noise reduction in Adobe Camera RAW. The difference is not seen when using low ISO values, but absolutely using high ISO. Interesting to notice is that the noise of high ISO images are more blotchy and more coarse within Adobe Camera RAW when noise reduction is set to zero, than in Capture NX2. But as soon as you use some noise reduction within Adobe Camera RAW, the reduction is far better than by the algorithms used in Capture NX2.

How this all work out to astrophoto images I am not familiar about it.

[Charles Krebs]

. Yet the above assertion is a concern since I occasionally do make long (> 30 sec) exposures and I would like to have the option to make long-exposure, star-filled night sky photographs. Although I mostly shoot macro, I don't want to be limited with respect to other specialty photographic explorations.

This is not really a concern for the use you mention. "Astrophotographers" will take many (sometimes hundreds) of images of the exact same sky scene. These are then processed together. Since noise is "random" but a faint star should appear in exactly the same location in every frame, the software used can determine what is "noise" and what is an actual object (i.e. faint star). In each individual image you would not be able to discern the faint star from the noise.

In any event, I think the consensus is that, despite some early concerns, there is no noise reduction actually done to the raw data. (But you need to pay attention to your conversion software settings.... many have a way of "sneaking " some in there as a default setting). If I recall correctly there was some noise reduction done to the in camera (D3) jpgs that could not be entirely eliminated even if NR was turned off, but it did not affect the raw files. Is was mild and only at very high ISOs (over 6400). I don't know for sure what the situation is with these new Nikon bodies, but I would suspect they don't mess with the raw files.

[Oskar O]

As Charles points out, the existence of noise reduction only matters when the intent is to take tens or hundreds of images and exposure stack them so as to reduce noise and enhance dynamics. And if that is to be done, the best results are anyway achieved using dedicated CCD astrocameras, although a regular DSLR can give good results in the right hands.

[Joaquim F.]

A test of D3 and D300 in astronomic imaging:
http://astrosurf.com/buil/nikon_test/test.htm
Both apply noise reduction in NEF files with all "switches" OFF even at low ISOs, my D300 start to "pixel cleaning" at 1/4 s. and longer exposures, I have no information about new cameras.
Canon seems the brand for astronomic images, including two special bodies without IR filters 60Da 20Da.

Regards