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Gromit44

UK
730 posts

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Gromit44 Registered since 04th Jan 2012
Mon 19-Nov-12 01:10 PM

Having seen a few comments on the internet, I'm wondering if Long Exposure Noise Reduction reduces overall image detail (as well as noise).

In other words, is is better to shoot with LENR off and shoot a separate dark frame for later use (the dark frame could be subtracted selectively in Photoshop instead of being applied to the whole image).

What do we think folks?

blw

Richmond, US
28708 posts

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#1. "RE: LENR on or off?" | In response to Reply # 0

blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004
Mon 19-Nov-12 02:13 PM

No, it doesn't do noise reduction in the traditional sense, so it does not reduce detail. It's strictly a color thing - it does a dark frame subtraction, and since the dark frame should be totally black, it removes everything that is actually IN the dark frame - and that's color subtraction.

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Brian... a bicoastal Nikonian and Team Member

My gallery is online. Comments and critique welcomed any time!

blw

Richmond, US
28708 posts

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#2. "RE: LENR on or off?" | In response to Reply # 0

blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004
Mon 19-Nov-12 02:14 PM

The dark frame is not used 100% without modification - by definition it is being done later in time and therefore with greater heat build up than the main exposure. The camera has firmware that accounts for the difference, so at least in theory it should be more accurate than doing it later in Photoshop.

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Brian... a bicoastal Nikonian and Team Member

My gallery is online. Comments and critique welcomed any time!

aay

CA
172 posts

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#3. "RE: LENR on or off?" | In response to Reply # 2

aay Registered since 11th Jul 2010
Mon 19-Nov-12 02:37 PM

Good to know, because I was wondering if there is more noise in the dark frame since the sensor runs that much longer/hotter.

Alex
http://www.yermakov.net

Antero52

Vantaa, FI
2683 posts

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#4. "RE: LENR on or off?" | In response to Reply # 2

Antero52 Silver Member Awarded for his expertise in post-processing, being  consistently helpful and professional. Nikonian since 07th Jul 2009
Mon 19-Nov-12 04:04 PM

Brian,

A problem with LENR is that doubles the time to take each photo. Sometimes when I realize that the photo will not be what I wanted, it is frustrating to wait for a 30-sec exposure to complete and then wait another 30 seconds for the LENR image. Do you think I can get equivalent results by taking just one 30-sec exposure with the lens cap on and subtract that from my good photos in Photoshop?

Regards, Antero

jamesvoortman

Durban, ZA
1479 posts

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#5. "RE: LENR on or off?" | In response to Reply # 4

jamesvoortman Silver Member Nikonian since 06th Sep 2004
Mon 19-Nov-12 04:31 PM

What happens if you switch off the camera and then back on again?

does it abandon the shot? this could be quicker than waiting the 30 sec, provided it does not cause problems.

To my mind, LENR has a hugely beneficial effect so I would rather have it enabled. I have set up one of my Shooting Menu banks with settings adjusted for poor light/long exposure/tripod mounted. LENR is enabled only in this bank.

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Gromit44

UK
730 posts

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#6. "RE: LENR on or off?" | In response to Reply # 5

Gromit44 Registered since 04th Jan 2012
Tue 20-Nov-12 01:17 PM

If the camera is switched off while "Job nr" is flashing, the pic will be recorded but NR won't be performed (manual page 277).

aay

CA
172 posts

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#7. "RE: LENR on or off?" | In response to Reply # 4

aay Registered since 11th Jul 2010
Tue 20-Nov-12 02:02 PM

Antero,

Here is a link that provides some details on this technique:

http://forums.dpreview.com/forums/post/41059442

And 30-sec exposure is not that bad - wasting extra 30 seconds is nothing compared with a sunset shot of 6-8 minutes when you see that lighting has changed but you have just started NR job which won't finish for the next 6-8 minutes..

Alex
http://www.yermakov.net

G