reaction time compensation - Feature Requests - CHDK Forum
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reaction time compensation

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Offline richard.y

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reaction time compensation
« on: 02 / May / 2009, 09:04:42 »
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I used to have an Olympus Camedia E-100 which had a "Pre-Capture" mode takes up to 5 photos before you press the shutter! The five pictures were continually updated so pressing the shutter took 5 pictures just before the shutter was pressed. This allowed pictures of sudden events, that have usually gone by the time you press the button, to be taken. This was useful for thinks like breaching whales, and boiling mud and jumping salmon. Is there any way that this could be implemented or are buffers not big enough.
Richard
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Offline fudgey

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Re: reaction time compensation
« Reply #1 on: 09 / May / 2009, 03:01:47 »
Well, if video mode quality is enough, this is theoretically possible. But since you could just as well shot video, I can see no point. The other option is to write a script that shoots at max speed timelapse (in continuous mode if no autoexposure or focus is required between shots) and deletes images older than 5 shots and stops when you press the shutter. All images will be written on the SD card and then deleted. Currently file deletion from Lua has some unwanted consequences (because we don't know how to tell Canon firmware that they are gone), but it should work.
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Offline richard.y

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Re: reaction time compensation
« Reply #2 on: 12 / May / 2009, 08:11:32 »
I agree that video mode is pointless. The problem with the timelapse solution is that the last picture could have been taken nearly as long ago as it takes to write a frame to the SD card, which is perhaps longer than reaction time in the first place, and if you had to wait long there is a good chance the card would be full before the event happened. For this to work the images need to remain in the buffer, rotating on a first in over-written basis, (I imagine that the 5 shots on the E-100 was the size of its buffer) and the shots would need to have been converted to jpg to be small enough for this to work.  I imagine this all makes it impossible, or at least impractical, but it would have been nice.
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Offline fudgey

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Re: reaction time compensation
« Reply #3 on: 12 / May / 2009, 13:45:33 »
We don't know a memory are large enough to store full images in them between shots. Well, actually a few low resolution, low quality JPEGs could probably fit in currently allocateable RAM of some (but not all) camera models (or maybe some spare play mode display buffer in some models), but even that probably requires a lot of hard work trying to disable writing those JPEGs to the SD card while still retaining them in RAM.
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