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Usefulness of AutoGain feature on Multiple Exposure??

Bravozulu

Los Angeles, US
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Bravozulu Registered since 04th Jun 2012
Tue 15-Jan-13 07:29 PM

How often is this feature used and what is its application?

Looks pretty much like rocket science.

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gkaiseril

Chicago, US
6739 posts

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#1. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 0

gkaiseril Gold Member Nikonian since 28th Oct 2005
Tue 15-Jan-13 06:40 PM | edited Tue 15-Jan-13 06:42 PM by gkaiseril

Do you want the make a double exposure in which you overlay your first image?

Without it, the fist exposure will look washed out or like a ghost under the second exposure.

Post-processing and staking of images might provide a better result.

George
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blw

Richmond, US
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#2. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 0

blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004
Tue 15-Jan-13 09:37 PM

My advice is to try it both ways. Usually when I'm doing multiple exposures, I use auto gain, since often one wants all of the various contributing exposures to be semantically equal. But sometimes I really do not want the exposures to be equal, so it's easier to get the correct result without auto gain. That means doing some calculation, usually mentally, and that can be pretty error prone. At least it is for me. But virtually any multiple-exposure image, at least in my experience, is a very deliberate kind of thing, and there is nearly always ample opportunity to reshoot if I get the calculations wrong.

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Bravozulu

Los Angeles, US
762 posts

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#3. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 2

Bravozulu Registered since 04th Jun 2012
Tue 15-Jan-13 11:45 PM

But why use multiple exposures in the first place? I don't want to be Man Ray with his photo collages.

I thought it was a remedy for high noise when shooting in dark places. Camera on a tripod. Two or three underexposed (intentionally) images, each having little noise. But adding up to correctly exposed, and noiseless single image. I guess this would suggest high ISO, or long shutter speeds.

I'm asking, because I don't know a thing about his and just came across a posting discussing some of the little-known treasures in the D7000 Shooting Menu.

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JosephK

Seattle, WA, US
7065 posts

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#4. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 3

JosephK Silver Member Fellow Ribbon awarded for his excellent and frequent contributions and sharing his in-depth knowledge and experience with the community in the Nikonians spirit. Nikonian since 17th Apr 2006
Tue 15-Jan-13 11:57 PM

>But why use multiple exposures in the first place? I don't
>want to be Man Ray with his photo collages.
>
>I thought it was a remedy for high noise when shooting in dark
>places. Camera on a tripod. Two or three underexposed
>(intentionally) images, each having little noise. But adding
>up to correctly exposed, and noiseless single image. I guess
>this would suggest high ISO, or long shutter speeds.

This would be an interesting experiment as I have not heard of this use before.

I have heard that you can use the multiple exposures to get the milky water effect when you cannot get the single long exposure.

---------+---------+---------+---------+---------+
Joseph K
Seattle, WA, USA

D700, D200, D70S, 24-70mm f/2.8, VR 70-200mm f/2.8 II,
50mm f/1.4 D, 70-300mm f/4.5-5.6 VR, 18-70mm f/3.5-4.5 DX

Chris Platt

Newburg, US
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#5. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 2

Chris Platt Silver Member Nikonian since 30th Sep 2012
Wed 16-Jan-13 04:13 PM | edited Thu 17-Jan-13 02:08 AM by Chris Platt

What is the advantage of doing this in camera instead of stacking the images in post?

EDIT: After seeing Brian's post above, I get it. Thanks.

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Bravozulu

Los Angeles, US
762 posts

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#6. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 5

Bravozulu Registered since 04th Jun 2012
Wed 16-Jan-13 04:54 PM

I don't know the advantage. That's why I'm asking about this feature.

Moreover, some of us do no PP modification. I don't have a computer that will run the modern programs. At least, not yet.

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briantilley

Paignton, UK
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#7. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 6

briantilley Gold Member Deep knowledge of bodies and lens; high level photography skills Donor Ribbon awarded for his support to the Fundraising Campaign 2014 Nikonian since 26th Jan 2003
Wed 16-Jan-13 05:06 PM

>Moreover, some of us do no PP modification.

There's your answer - the Multiple Exposure facility can be useful for people who want to combine images - say, a full moon into a featureless dark sky - but like to do as much as possible in-camera in an automated way.

Brian
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Chris Platt

Newburg, US
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#8. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 7

Chris Platt Silver Member Nikonian since 30th Sep 2012
Wed 16-Jan-13 10:03 PM | edited Thu 17-Jan-13 12:50 PM by Chris Platt

Yes, that occurred to me shortly after I posted the question. Thanks.

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blw

Richmond, US
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#9. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 3

blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004
Wed 16-Jan-13 10:28 PM | edited Wed 16-Jan-13 10:44 PM by blw

> But why use multiple exposures in the first place? I don't want to be Man Ray with his photo collages.

There's more than one way to use multiple exposures.

Click on image to view larger version


Click on image to view larger version


Click on image to view larger version


Yes, it is possible to do this in post. One reason I do some of these this way, frankly, is that I'm tired of the criticism I sometimes get for "non-photography." So for things like this, I sometimes do it in-camera. Honestly, it's really a terrible reason. I should just do it the way that's best, and forget what other people say. In these three cases, it's probably just as good or possibly even better to do it in the field with the camera. I'd say it's better to do it in-camera since one can easily judge the result in the field and reshoot. Each of these is one of a number of attempts - usually four or five at a time - and they're not exactly precision craft. This is particularly true of stuff like #2 which might be emphasizing things like flowers blowing in the wind.

> I thought it was a remedy for high noise when shooting in dark places.

You could do that, although it's better to do it with some other software, which assumes that the images are supposed to be equal, thus eliminating noise - which would be different in every exposure. Sort of like the Fuji x10/x20 do.

The difference between that and your proposal is that you're assuming a tripod, but frankly if you can do that, you can probably just expose it properly in the first place.
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Bravozulu

Los Angeles, US
762 posts

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#10. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 9

Bravozulu Registered since 04th Jun 2012
Wed 16-Jan-13 11:11 PM | edited Wed 16-Jan-13 11:14 PM by Bravozulu

Beautiful, beautiful, beautiful. That's all I can say. We get all the 'realism' we need on the evening news. Artistic vision is sadly lacking. And one of the seductive delusions of photography is that we are accurately recording the reality around us with our cameras.
Bank clerks keep accurate recordings of reality and, in my case at least, the results are not inspiring.

It is an old argument. Realism versus imagination. I didn't mean to put down Man Ray in my earlier post. My professor of photography at UCLA in the early '60s was Edmund Teske (of Chicago). He studied with Man Ray, and was a resident at Taliesin West with Frank Lloyd Wright for 10 years. Cold photographic realism is too easily usurped by journalism. That's what the wisdom he urged in his young students. Who were, in the main, architecture students.

I applaud a photographer imposing his ideas on realism. In the camera. In post. In a darkroom with smelly chemicals. It's all good.

Thanks, I've learned more than I had hoped for.

Gary - Santa Monica

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Bravozulu

Los Angeles, US
762 posts

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#11. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 8

Bravozulu Registered since 04th Jun 2012
Thu 17-Jan-13 02:27 AM

This is the photo that prompted me to post a question. It came on the D7000 Tips forum. And included descriptive text on how the image was achieved. Multiple images shot at reduced exposure. Merged with Auto Gain turned on.

The camera, by the way, had no noise reduction set. Photos were merged in the camera. No post.

Click on image to view larger version

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jeffcs

Whiting, US
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#12. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 11

jeffcs Silver Member Nikonian since 15th Jan 2009
Thu 17-Jan-13 07:17 AM


Bravozulu
Might be helpfull for a bunch of us if you could post a link to the D7000 how-to
I love the image of the boats in the harbor

Thanks

Jeffcs

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blw

Richmond, US
28561 posts

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#13. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 11

blw Moderator Awarded for his high level of expertise in various areas Nikonian since 18th Jun 2004
Thu 17-Jan-13 08:46 AM

Again, I'm hard-pressed to imagine how this would be better than simply getting the exposure right in the first place. You'll have motion artifacts either way. Shooting it at base ISO - and correct exposure - will surely result in no more noise than a regular daytime snapshot.

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Bravozulu

Los Angeles, US
762 posts

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#14. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 13

Bravozulu Registered since 04th Jun 2012
Thu 17-Jan-13 02:55 PM

Here's a link to the original tip. Scroll down to Tip #7.

http://forums.photographyreview.com/nikon-camera-equipment/nikon-d7000-tips-78038.html

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elec164

US
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#15. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 13

elec164 Silver Member Nikonian since 15th Jan 2009
Thu 17-Jan-13 03:08 PM | edited Thu 17-Jan-13 03:25 PM by elec164

>Again, I'm hard-pressed to imagine how this would be better
>than simply getting the exposure right in the first place.
>You'll have motion artifacts either way.

Actually if that sample was a multiple exposure merge, it's pretty good in that there is to me little appearent motion artifacts especially in the masts.

But there is an advantage in stacking multiple shots with regard to SNR I believe.

The predominate noise source in images is shot noise. The benefit of multiple stacking is that the stronger signal will be accumulative and show little difference, but the lower signal will be averaged and shot noise would be improved (especially in fine gradient areas such as the sky).

At least I think I got that correct!!

Pete

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jbloom

Wethersfield, US
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#16. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 15

jbloom Gold Member Awarded for the continuous and generous sharing of his high level expertise and his always encouraging comments in several forums. Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014 Nikonian since 15th Jul 2004
Thu 17-Jan-13 03:24 PM

Pete, I believe you have the theory correct, but the question -- and I think this is what Brian is driving at -- is whether the SNR will be reduced more by taking three high-ISO shots and merging them compared to taking one low-ISO shot, albeit at a longer exposure. Either way, you have to consider motion effects. Either way, you'll improve the SNR. I think the jury is out as to which way would be better, but I'm with Brian in thinking you probably won't gain that much with the multiple-exposure technique.

-- Jon
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elec164

US
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#17. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 16

elec164 Silver Member Nikonian since 15th Jan 2009
Thu 17-Jan-13 03:59 PM

>-- and I think this is what Brian is driving at -- is whether
>the SNR will be reduced more by taking three high-ISO shots
>and merging them compared to taking one low-ISO shot, albeit
>at a longer exposure.

I think it depends on what the Gain in “AutoGain” means.

You are taking it to mean ISO or A/D amplification where it could mean a setting in post capture processing.

For example I shot these test images at base ISO of 100 (the D7000 has no Lo ISO settings).

This is single capture.

Click on image to view larger version


This is a three shot multiple exposure with AutoGain enabled.

Click on image to view larger version



They are NEF's using LR3 for conversion, using the Auto button (there was an apparent difference in exposure between the two) and a 71 sharpening setting only. Then I handed off to PS for cropping to 100% and saving.

To me there is significant difference in the darker background.

This technique has been used in Astrophotography for some time to improve overall image quality. The only limitation I see with the in camera process is that you are limited to only 2 or 3 shots. In Astrophotography they might often use 10 to 30 exposures (or more).

Pete







Attachment#1 (jpg file)
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Pete

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elec164

US
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#18. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 3

elec164 Silver Member Nikonian since 15th Jan 2009
Thu 17-Jan-13 05:33 PM

>Two or three underexposed (intentionally) images, each having little noise. But adding
>up to correctly exposed, and noiseless single image.

I don't believe that's necessarily so.

There are two types of noise, fixed pattern and random. Shot noise is random and best dealt with through blended multiple exposures. But while several underexposed images might improve shot noise, I believe it will make fixed pattern noise such as read noise more apparent.

So in that sense it won't be noiseless, but instead random noise will be improved while fixed pattern noise will be worsened.

At least I think I got that correct.

Pete

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jbloom

Wethersfield, US
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#19. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 17

jbloom Gold Member Awarded for the continuous and generous sharing of his high level expertise and his always encouraging comments in several forums. Donor Ribbon awarded for his generous support to the Fundraising Campaign 2014 Nikonian since 15th Jul 2004
Thu 17-Jan-13 05:51 PM

Interesting. I'll have to play with that. I must say, though, that I'm not used to seeing that much noise from the D7000 at ISO 100.

-- Jon
Wethersfield, CT, USA
Connecticut High School Sports Photos

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elec164

US
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#20. "RE: Usefulness of AutoGain feature on Multiple Exposure??" | In response to Reply # 19

elec164 Silver Member Nikonian since 15th Jan 2009
Thu 17-Jan-13 07:58 PM | edited Thu 17-Jan-13 08:07 PM by elec164

>Interesting. I'll have to play with that. I must say, though,
>that I'm not used to seeing that much noise from the D7000 at
>ISO 100.
>

Don't forget that is a 100% crop. That's like looking at a door sized print from an 8x12 viewing distance. Under normal viewing and printing that noise would not be visible.

Pete

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G