I have seen many folks (including Hogan)recommend that Long Exposure NR on the Shooting menu be turned on for exposures over one second. Is this still true if you are shooting an HDR set at low ISO and the higher EV frames cause the camera to have shutter speeds over 1 second?

Larry Jordan

D800E, 14-24, 50, 24-70, 70-180 Micro, 70-200, 80-400mm AF-S

Website:
http://larryjordan.smugmug.com/

Hey, you guys must be buried in Thom Hogan's new D800 book...cause I got no rise outa ya with my NR & HDR question.

So, I ran my own test in the garage as the sun was coming up. I shot 9 frames at 1EV change per frame...-4EV to +4EV. I shot them with Long Exposure NR off, and then again with it on. Here are the differences:
- It took substantially longer to shot the 9 frames with NR on because of the additional processing required for the long exposures before the frames are stored
- I got the "Job nr" message on the LCD in between the long exposures
- There was no difference in HDR image detail or noise when processed with CS6 Merge to HDR
- There was some slight color artifacts when NR was turned on

Thus, I will always keep Long Exposure NR turned off unless I am shooting a single long exposure frame.

Larry Jordan

D800E, 14-24, 50, 24-70, 70-180 Micro, 70-200, 80-400mm AF-S

Website:
http://larryjordan.smugmug.com/

>- There was no difference in HDR image detail or noise when
>processed with CS6 Merge to HDR

I think that at 1 second you are at the very bottom of when LENR is useful.

Try your same test at 30 seconds and I suspect you would see a benefit from it (and of course much longer time to process -- it takes another exposure with the shutter closed for each exposure with it open).

LENR reduces thermal noise which is (somewhat) proportional to exposure length. The longer the more noise.


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What I meant was, for any exposure over one second. When I shot HDR in my garage this morning, my longest exposure was 8 seconds.

Larry Jordan

D800E, 14-24, 50, 24-70, 70-180 Micro, 70-200, 80-400mm AF-S

Website:
http://larryjordan.smugmug.com/

I keep it turned off too, the processing takes too long and I haven't seen any benefit.
Dave Jolley

Visit my Nikonians gallery.

It's not "processing" that takes so long with LENR. The camera actually does another exposure, same duration as the first, but with the shutter closed. It then subtracts this "black frame" exposure from the original, thereby removing any pattern noise created consistently by the sensor.

I agree with others, 1" is probably not all that critical for LENR. But, bear in mind, if you're doing a 20" exposure, the "processing" will take an additional 20" while your camera will be tied up with "Job NR" the entire time.

For this reason, you should NEVER use LENR when doing composite images, unless you have absolutely no chance of subject motion whatsoever.

But, if long exposure noise is a problem and you're trying to do a composite image, not all hope is lost. This most commonly occurs when shooting star trails, and trying to stack several 5 minute (or so) exposures. Here long exposure noise is a problem, and 5 minute gaps in the star trails would be completely unacceptable. What star trail shooters do, is fire off all the composite images, then take a single "dark frame" the same duration as the other shots, with the lens cap on. Then, software can be used in post processing to subtract this pattern noise frame from all the images in the composite. Seach on digital star trail techniques to learn more details on these techniques. Then, you can apply them to your HDR if necessary, but like others have said and your test shows, probably overkill for 1" exposures.

Larry - a Bay Area Nikonian
My Nikonians gallery

www.tempered-light.com