huge delay after photo taken - Script Writing - CHDK Forum

huge delay after photo taken

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huge delay after photo taken
« on: 16 / September / 2009, 00:22:01 »
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Hello,  I am using Long exposure night shot script by cyril42e and getting wonderful results, but dont understand why that once the picture is taken and I try to quit out of ALT mode the camera goes into a busy state with a icon stop hand for almost as long as it took to take the photo.  This does not happen with other scripts (that i am aware of) 

When I am standing out on a mountian side at midnight 2 miles from the nearest road, and things are moving around my feet and larger things bushes, Id rather not be standing around waiting for the camera to do nothing if it aint doing something important.   
:o

I am using a SD750 camera


taken during the SoCalif fires

the script i am using is as follows:

rem Author: cyril42e <cyril42e@gmail.com>
rem Camera: SD1000_IXUS70 and DIGIC III cameras
rem Camera: For DIGIC II, replace set/get_prop 207->26, 206->205
rem Description: Auto sets long exposure (> 1") for night shots with tripod, with 2s delay
 
@title Long exposure night shot
 
rem prepare the shot : shoot_half and wait ready
press "shoot_half"
do
   get_prop 206 c
until c=1
rem read bv (luminance), sv (iso speed), av (aperture), and ev shift
get_bv96 b
get_sv96 s
get_av96 a
get_prop 207 e
rem set tv (exposure time) : tv = bv + sv - av (- ev) (apex)
get_tv96 t
print "old tv96:",t
t=b+s-a-e
print "new tv96:",t
set_tv96_direct t
sleep 100
release "shoot_half"
 
rem wait additional 2s and shoot with new exposure
sleep 2000
f=get_tick_count
shoot
g=get_tick_count-f
print "shot length",g,"ms"
 
end

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Offline reyalp

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Re: huge delay after photo taken
« Reply #1 on: 16 / September / 2009, 00:30:46 »
Hello,  I am using Long exposure night shot script by cyril42e and getting wonderful results, but dont understand why that once the picture is taken and I try to quit out of ALT mode the camera goes into a busy state with a icon stop hand for almost as long as it took to take the photo.
This is canon's dark frame subtraction, which is enabled by the canon firmware for long exposures. You can force it off (either in raw options or in script) but unless you do your own dark frame subtraction later in processing, quality will be significantly reduced.
Don't forget what the H stands for.

Re: huge delay after photo taken
« Reply #2 on: 16 / September / 2009, 20:01:26 »
thanks.  i'll watch it a tad more, but it only seems to kick in once i have tried to stop the process and see if I can confirm it's a camera doing something or when i fiddle with the buttons   thank again

Re: huge delay after photo taken
« Reply #3 on: 16 / September / 2009, 20:21:07 »
dont know if your correct, assume you are, and i am wrong it wasnt my playing with the buttons it just took a few seconds to kick off whatever this canon process is and then waiting for this to complete.  seems like forever when animal runs across your boot. 



thanks


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Offline reyalp

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Re: huge delay after photo taken
« Reply #4 on: 16 / September / 2009, 20:32:02 »
thanks.  i'll watch it a tad more, but it only seems to kick in once i have tried to stop the process and see if I can confirm it's a camera doing something or when i fiddle with the buttons   thank again
The camera showing "busy" and being unresponsive for exactly the same length of time as the exposure just taken is almost certainly dark frame subtraction. Google "dark frame subtraction" if you are unfamiliar with this.

AFAIK on powershots this is generally done for exposures longer than something like 3 seconds, but may also depend on things like ISO setting and sensor temperature.
Don't forget what the H stands for.

 

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