D70s - Long exp. NR

[shibolim]

I'm slightly confused with this feature.

According to the manual (and the tests I've done), enabling long exposure NR performs NR on pictures taken at shutter speeds slower than 1 second, yet the continuous shooting FPS rate drastically decreases - regardless of shutter speeds of the pictures taken.

Did I get it right? Can someone figure out the rationale behind this? Or, in other words, is this a bug or a feature?

P.S. this is my first DSLR - a used D70s + 18-135 which I recently bought

( http://forums.dpreview.com/forums/readflat.asp?forum=1034&thread=25079087 --- thanks for all your advices), so expect many questions and maybe a picture post or two...

 

[john Clinch]

What is happening is that each shutter release takes two exposures, one with the shutter open, the other with the shutter closed. The dark frame is subtracted from the exposure.This helps to reduce noise, espeically noise due to uneven heating. Obviously it takes quite a long time for both exposures and the processing.Its aimed at 15 seconds on a tripod not continuous shooting
--
http://www.photo.net/photos/JohnClinch
http://www.flickr.com/photos/john_clinch/

If any post processing is required I find it easier to start from the RAW file.

 

[wijnands]

Just as I experienced it with the D50. According to Thom Hogan this is ment to compensate for noise caused by the heating up of the sensor. Personally I only use it for long exposures at night.
--
Don't wait for the Nikon D-whatever, have fun now!
http://www.flickr.com/photos/j_wijnands/

 

[shibolim]

Yeah, but (if I understood the manual correctly) this feature does not apply for images taken at speeds faster than 1 sec.

For example, shooting at 1/125 sec with long exposure NR enabled, the camera does not take reference images and does not perform NR. However continuous shooting rate will be significantly slower than 3 FPS.

 

[Thomas Comerford]

According to Nikon, once you enable Long Exp. NR the camera has to change the way the internal buffer is allocated and apparently this is responsible for the slowdown in continuous shooting.

My own personal theory is that the buffer isn't a random-access device, so if you take a shot at a high shutter speed the camera reads the raw data from the buffer and processes it into an image but it then has to "read through" the part of the buffer that would contain dark frame data regardless of whether a dark frame was recorded or not, and this slows the camera down slightly.

Yeah, but (if I understood the manual correctly) this feature does
not apply for images taken at speeds faster than 1 sec.

For example, shooting at 1/125 sec with long exposure NR enabled, the
camera does not take reference images and does not perform NR.
However continuous shooting rate will be significantly slower than 3
FPS.

--
http://www.pixelfixer.org

 

[john Clinch]

Good point. It vaguely drifted through my mind that the buffer would be needed for dark frame subtracion, well it got to keep the first frame some where. I'll turn it off when i get home.....
--
http://www.photo.net/photos/JohnClinch
http://www.flickr.com/photos/john_clinch/

If any post processing is required I find it easier to start from the RAW file.

 

[shibolim]

It makes sense.

So it's better to keep NR disabled for daily use, turning it on only for long exposures.

Thanks.