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Old Feb 23, 2006, 3:38 PM   #1
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Hi,

I am not pleased with the amount of time I have to wait after a long exposure shot.
It gets most annoying, if the shutter time is 2s and longer. Then there appears a "Please wait..." message, wich takes exactly one more shutter time. If you select 30s the it forces you to wait another 30s. The same goes for 60s andof course all the other settings.

I would really like to know what the camera does during that time... I mean, this can't be real... Exactly the same time that was set for the shutter every time. What for?

Is there any possibility to avoid it?

Thanks a lot!

Pit
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Old Feb 23, 2006, 3:52 PM   #2
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The "Please wait" message you see is because after each shot (no matter - fast or slow) the camera make another one with closed blend - in this way it have the "black" shot. Using both it removes the dead pixels (if any) on the CCD.

As I know there is no way to turn off the "black" image (at least on my FZ20)
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Old Feb 23, 2006, 4:23 PM   #3
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Alright, I understand that this has t be done. But where is the difference between taking a black picture for 60s and taking it for 1s or even less?
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Old Feb 23, 2006, 4:33 PM   #4
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The difference is in the noise of the CCD. The longer the expose is the noise is more.
Make this test
Take a long expose shot 8s is enought.
then take the same shot but with the lens cap on it
compare the shots - see that the noise in the seccond shot is MUCH less.
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Old Feb 23, 2006, 8:39 PM   #5
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Of course it is less noisy with the lens cap on it, but I don't understand, why it has to take that long for the shutter-closed-shot. That would mean, that there is an enormous amount of data stored on some big built-in memory chip that has to be readjusted with the noiseless shot with the shutter closed.

I just don't get, where the difference lies. I have never seen this curiosity on any other camera before.
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Old Feb 23, 2006, 9:03 PM   #6
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Is called dark frame subtraction and all cameras do it to one extent or another, even the 2000 dollar ones

http://www.kenrockwell.com/nikon/d200/d200-dark.htm
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Old Feb 23, 2006, 9:21 PM   #7
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Oh now I got it.

The camera has to substract the noise that is visible with the closed shutter for the same amount of time as it has been added during exposure.

But then I must ask, why can't this be done more efficiently? I don't think that the noise that is recorded while the shutter is closed does change dramatically during the 60 seconds (or even less). So why can't they just record it for 1 second and multiply it with the amount of seconds that was set for exposure?

At least I know now, what it does and how. Only that I don't really like the idea of waiting many minutes during a nightly photo session outdoors in the cold

Thanks a lot to both of you!
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Old Feb 25, 2006, 9:38 AM   #8
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Thanks for the link, genece.

The waiting time has bothered me about my FZ10 also... now I *hope* I'll understand why.
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Old Feb 25, 2006, 12:18 PM   #9
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Leberwurstsaft wrote:
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Oh now I got it.

The camera has to substract the noise that is visible with the closed shutter for the same amount of time as it has been added during exposure.

But then I must ask, why can't this be done more efficiently? I don't think that the noise that is recorded while the shutter is closed does change dramatically during the 60 seconds (or even less). So why can't they just record it for 1 second and multiply it with the amount of seconds that was set for exposure?

At least I know now, what it does and how. Only that I don't really like the idea of waiting many minutes during a nightly photo session outdoors in the cold

Thanks a lot to both of you!
the noise in the CCD depend on many factors. It is not possible to record the 1s expose noise and multiply it because the increase in noise is not linear.
For example the enviorment temperature cause change in noise too. If you take a shot just after the camera starts and another one after 20minutes (withot turning off the camera you will see the changes in the noise). So to have effect the dark frame, it must be taken at the same "situation" as the picture that must be processe.
Be sure that if there was a way to "remove" this long "please wait" problem the camera makers "know" about it and will use it to "kill" the other camera makers


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Old Feb 25, 2006, 12:25 PM   #10
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Alright, hehe. Understood.

But, what about those dslr cameras that can take a 10 minutes shot? I can't imagine, that they have to wait 10 minutes, too. But I guess they just aren't that noise sensitive...
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