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"large" bracketting and camera crashing ..

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Offline nickie

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"large" bracketting and camera crashing ..
« on: 29 / January / 2010, 05:45:00 »
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hey !
last question, i'm not going to pollute the board with all my newbie problems, but here i a talking about my SX200IS again:


yesterday i did some bracketting tests, and to my surprise, i found the camera hung up , froze, on the last pictures i expected it to do, so much that after 20 minutes i gave up, took off the battery and restarted the thing: the last picture was not recorded,

i had tried to make night shots with 2Ev bracketting over 6 pics; and my guess is that i asked the camera to go too far in ev correction so it froze,

today i then tried to make further tests, took a sequence of 10 picture, with only 1/3ev difference, and it worked as i expected it to

all these tests done in manual mode

so is asking the camera to go over a certain EV correction thru bracketting a dead end ? is there a way to avoid the software crash with shutterspeed override or something?

thanks! :)
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Offline barret

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Re: "large" bracketting and camera crashing ..
« Reply #1 on: 29 / January / 2010, 08:07:51 »
I'm not entirely sure if camera really hangs. maybe it's taking the shot?
i experienced very long camera hung ups, which turned up to be in fact very long exposure.
think of it: when you make bracket series in mid/low light conditions, and camera tries to make highly overexposed picture, time required to do this might be very long.

it's a good idea to check camera settings when starting bracketed series. then you can estimate how log the longest exposure might become. for example, if you're making +-4ev and base time is 1 sec, longest exposure might be well over 5 minutes (which is quite long to just stand there and wait).
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Offline nickie

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Re: "large" bracketting and camera crashing ..
« Reply #2 on: 29 / January / 2010, 09:03:31 »
yeah well i first thougt it was taking the shot, but half an hour seemed quite long to me i'll make more tests and try to calculate if it can go that long with my settings,

what worries me was that there are basically 2 camera states, one showing the previous image, and one showing "BUSY" both separated by a shutter click , i guessed one would be taking the shot, and the other one would be processing the picture, but they BOTH grew longer over shots and it made me suspicious indeed


but it's true that i attempted a night shot on 80ISO so i expected LOOONG exposure indeed so i'll find out how far it actually goes :D

thanks :D
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Offline Microfunguy

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Re: "large" bracketting and camera crashing ..
« Reply #3 on: 29 / January / 2010, 09:31:34 »
Quote from: nickie on 29 / January / 2010, 05:45:00
i had tried to make night shots with 2Ev bracketting over 6 pics

You do not say if the exposures alternate, are shorter or longer.

Do you understand what an EV change of 2 means ?
It means the exposure is 4x longer or shorter than the current one.
With six exposure, the last one is 1000x longer or shorter than the first one (if CHDK is capable of that exposure).

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Offline fe50

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Re: "large" bracketting and camera crashing ..
« Reply #4 on: 29 / January / 2010, 13:26:48 »
Quote from: nickie on 29 / January / 2010, 09:03:31
what worries me was that there are basically 2 camera states, one showing the previous image, and one showing "BUSY" both separated by a shutter click , i guessed one would be taking the shot, and the other one would be processing the picture, but they BOTH grew longer over shots and it made me suspicious indeed
First the camera captures the image, then a dark frame is taken; this doubles the time, the camera shows "Busy" while doing this...
The SX200 CHDK version has the "extra long exposure" feature, exposures with over 2000s (> 33 minutes) are possible.

- Dark frame subtraction
- extra long exposure feature
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Offline nickie

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Re: "large" bracketting and camera crashing ..
« Reply #5 on: 30 / January / 2010, 05:03:36 »
Quote from: Microfunguy on 29 / January / 2010, 09:31:34

You do not say if the exposures alternate, are shorter or longer.
alternate :)

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Do you understand what an EV change of 2 means ?
well basically, not so much because i've been used to the good old 2EV max and the ability to go over 10 or whatever is quite new to me :)


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First the camera captures the image, then a dark frame is taken; this doubles the time, the camera shows "Busy" while doing this...
ah! so for every long picture i take, the camera spends the same time taking a dark frame ? well that's quite a great info to me, i now know why it can spend 10 minutes on "busy", thanks lots! :D

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Offline reyalp

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Re: "large" bracketting and camera crashing ..
« Reply #6 on: 30 / January / 2010, 16:35:59 »
You can disable canon dark frame subtraction in the CHDK menu. However, if you do that you'll probably want to do your own somewhere along the way to get reasonable quality.
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Offline nickie

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Re: "large" bracketting and camera crashing ..
« Reply #7 on: 31 / January / 2010, 03:41:03 »
well as i'm using that kind of bracketting to mix pics anyway i can use the darkest pics instead as noise reference anyways :)

i'll test :)
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