Bracketing During Exposure - Feature Requests - CHDK Forum
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Bracketing During Exposure

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Offline Flutterbudget

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Bracketing During Exposure
« on: 16 / December / 2011, 11:53:47 »
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Hey, I know this is a long shot, but I was wondering if bracketing (specifically SD bracketing) could be done DURING an exposure. Could this be scripted, would some serious hard work have to be done, or is it just not possible?


!Noah!
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Offline fudgey

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Re: Bracketing During Exposure
« Reply #1 on: 18 / December / 2011, 04:01:41 »
I don't remember if anyone's tried. Tv bracketing is obviously not sane during exposure, and the others are just kind of weird experiments. But all weird may of course result in funny photos.

See http://chdk.setepontos.com/index.php?topic=2518.0 for a simple example of how to zoom during an exposure. Instead of zoom, you may try changing the focus instead. And if set_focus stuff doesn't do anything, there might be eventprocs that do.

Be aware that this kind of weird experiments also often cause the camera firmware to crash. So don't have anything valuable on the memory card when you start and make sure you know how to remove the battery.
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Offline outslider

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Re: Bracketing During Exposure
« Reply #2 on: 18 / December / 2011, 08:02:50 »
Nice to see that kind of experiment;) I tried on SX130 and unfortunately this crashes. Camera starts exposure, then move zoom ant then exposer can't end. It takes over a dozen seconds and then camera crash.

Nevertheless it worked for focus;)
« Last Edit: 18 / December / 2011, 08:26:33 by outslider »
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if (2*b || !2*b) {
    cout<<question
}

Compile error: poor Yorick
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Offline Flutterbudget

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Re: Bracketing During Exposure
« Reply #3 on: 18 / December / 2011, 12:44:07 »
Hey! Thanks for the response. I found the Lua from the Zoom during exposure script, but, unfortunatly, I'm not familiar with Lua (or any other scripting language, for that matter). Could someone help me a bit with it?

Code: [Select]
--[[
Test zooming during long exposure.
 
1) Set camera to shoot a very long exposure (either M or Tv mode or
CHDK Tv override).
 
2) run the script
--]]
 
max_zoom = get_zoom_steps() - 1
 
if get_zoom() ~= 0 then
  set_zoom(0)
  sleep(5000)
end
 
press("shoot_half")
repeat
  sleep(1)
until get_shooting() == true
press("shoot_full")
sleep(100)
set_zoom(max_zoom)
 
repeat
  sleep(1)
until get_shooting() ~= true
 
release("shoot_full")
release("shoot_half")
 
!Noah!
« Last Edit: 18 / December / 2011, 13:05:34 by Flutterbudget »
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Offline waterwingz

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Re: Bracketing During Exposure
« Reply #4 on: 18 / December / 2011, 13:34:12 »
Quote from: Flutterbudget on 18 / December / 2011, 12:44:07
Hey! Thanks for the response. I found the Lua from the Zoom during exposure script, but, unfortunatly, I'm not familiar with Lua (or any other scripting language, for that matter). Could someone help me a bit with it?
Looks like it sets the zoom all the way out,  takes a picture,  sets the zoom all the way in and takes another picture.

What help did you want ?
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline outslider

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Re: Bracketing During Exposure
« Reply #5 on: 18 / December / 2011, 13:50:02 »
It works a little bit different (I tried exactly the same script).

It starts exposure (presses shot full) and then moves zoom to maximum. Lens are moving while camera takes exposure. Then exposure ends (read as: should end).

On my sx130 camera crashes...
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Offline waterwingz

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Re: Bracketing During Exposure
« Reply #6 on: 18 / December / 2011, 14:13:35 »
I see that now - here's shot out my window - F8,  ND filter in,  2 second exposure.


Update : I probably "cheated" here as I used the G10's manual overrides rather than the CHDK ones.
« Last Edit: 18 / December / 2011, 14:21:58 by waterwingz »
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Ported :   A1200    SD940   G10    Powershot N    G16
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Offline outslider

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Re: Bracketing During Exposure
« Reply #7 on: 18 / December / 2011, 15:25:07 »
I tried overrides too for shutter speed, but it also crashed. I'm wonder, what's different, and why some cameras crash when zoom is changed during exposure.

BTW - funny photo;) This technique could be used for some special staff. At the moment I used focus changes and photo had higher DOF (in fact whole area was a little bit blurry, but also focused)
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if (2*b || !2*b) {
    cout<<question
}

Compile error: poor Yorick
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Offline reyalp

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Re: Bracketing During Exposure
« Reply #8 on: 18 / December / 2011, 18:20:14 »
Quote from: fudgey on 18 / December / 2011, 04:01:41
Be aware that this kind of weird experiments also often cause the camera firmware to crash. So don't have anything valuable on the memory card when you start and make sure you know how to remove the battery.
I'd also suggest that hardware damage is not entirely out of the question. The camera is likely not expecting the zoom and focus mechanism to move during exposure.
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Offline Flutterbudget

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Re: Bracketing During Exposure
« Reply #9 on: 18 / December / 2011, 21:16:42 »
Hey! Thanks for all the response, again.

Waterwingz: my idea was mostly to change subject distance during the exposure to create (in my mind's idea) a lightpainting in which part of it is out of focus and part is in, not restrained merely to the obvious distance of the actual light(s) in the picture. It would have a sort of DOF/SD distortion effect, I think, and I'm not sure exactly what it would look like, so I'd like to try it.

reyalp: thanks for the warning. It seemed likely to me that this would be a possibility, but I think a previous poster (outslider) mentioned that they'd tried SD bracketing during exposure and had succeeded. If this is true, I'd like to know everything I could about that and try it myself. It'd be one strike against the idea that the camera could be damaged.

(my camera is an SD780, by the way.)

Thanks again, folks!


!Noah!
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