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Time lapse feasibility

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Offline jcarruthers

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Time lapse feasibility
« on: 03 / April / 2009, 11:13:16 »
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Hi all,


A friend and I are planning to make a time-lapse of an event we are taking part in. Last year he used his Canon DSLR to take hundreds of photos and this was the result:

vimeo.com/1913782[/vimeo]]http://www.Not a valid vimeo URL[/url]

That's approx 1 per second - obviously longer when it gets dark. The whole event is 48 hours - and he captured nearly all of it.

There is a slight issue with this though - as it means stopping the camera and downloading. He couldn't use it tethered because the download speed was too slow via USB.

So my question is; is CHDK feasible? We wouldn't be planning to use the DSLR again as it's quite noisy and obviously it's an expensive camera to wear out - my idea was to use something like one of the A series Powershots or perhaps a G series. Is CHDK stable enough to be shooting every 1 sec - fill up a 16Gb card - and then swap it over with another card. No issues copying them down to a laptop - 16Gb is about 4 hours? Or perhaps we will aim for a lower resolution this time.



James
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Offline wontolla

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Re: Time lapse feasibility
« Reply #1 on: 03 / April / 2009, 18:51:16 »
The short answer is yes, CHDK can make the camera take thousands of photos.
Regarding the resolution: If you are going to just put the video on the internet, then IMO there is no need for high resolution. The story is different if you want to display it on a big TV.
You might find these links interesting:

http://chdk.setepontos.com/index.php/topic,2589.0.html
http://chdk.setepontos.com/index.php/topic,3284.0.html
http://chdk.setepontos.com/index.php/topic,2634.msg24440.html#msg24440
http://chdk.setepontos.com/index.php/topic,1145.0.html
http://chdk.setepontos.com/index.php/topic,2556.msg23815.html#msg23815

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Offline PhyrePhoX

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Re: Time lapse feasibility
« Reply #2 on: 03 / April / 2009, 19:01:05 »
there are reports (dont know if wontolla linked to these) that indicate that the cameras are not built to record thousands of images in one session or better: onto one sdcard. imo it crashes after like 9000 pictures. this could be overcome by rebooting the cam and using scripts to move files or rename folders.
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Offline peabody

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Re: Time lapse feasibility
« Reply #3 on: 04 / April / 2009, 22:38:32 »
I've been working on CHDK timelapse with the A590IS.  But that was at a 4-second interval, and I stopped it after a couple thousand pics.  With that camera, I think the issue would be battery life.  You would probably need to switch out the batteries every three hours or so, or have an external power supply of some kind.

I've been shooting these at 1600x1200, but you could actually go all the way down to 640x480 if the video is going to be that small anyway.

I don't see any reason why it couldn't be made to work.  And it also seems much better to use a P&S as opposed to wearing out the mirror on your DSLR.
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Offline jcarruthers

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Re: Time lapse feasibility
« Reply #4 on: 05 / April / 2009, 04:24:48 »
Hi everyone,

Thanks for your replies.

Peabody you are right - I forgot that one of the things I need is a power adapter. Did your A590 stop because it ran out of batteries then?

Ideally I'd like to use somewhere between 1600x1200 and 640x480 - something like 1280x1024 etc I'd like something that I can run reasonably well on HD - looking to the future everything is in HD. The videos on Vimeo are amazing in HD.

Either that or I need a P&S that can run tethered quick enough - I'd think 640x480 would be ok.

Of course a webcam is ideal - but the quality isn't really good enough. (a P&S that can run as a webcam - perhaps that will work)

James
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Offline fudgey

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Re: Time lapse feasibility
« Reply #5 on: 05 / April / 2009, 06:03:02 »
This may be incorrect, but I'll say it anyway: to me it looks like each nnnCANON directory under DCIM costs 48000 bytes (2000 * 24) of RAM during a timelapse. A new directory is created after every 2000 shots or if IMG_9999.JPG is reached (yes that's right, my camera does not fill each nnnCANON directory during a timelapse).

If your camera is low in RAM (see http://chdk.wikia.com/wiki/CHDK/Camera_RAM_memory_usage#Available_RAM_by_camera_model and fill it up please), this may be very important for you. To me, it is the likely cause of my timelapse crashes on a570 running a complex Lua script when attempting to allocate RAM for a table for JPEGs of the fifth directory.

To squeeze the last drop of RAM, you could reset JPEG numbering before each timelapse session (and of course start out with a clean card) to save that 0 to 48000 bytes (usually 0, only non-zero if current image is IMG_8000.JPG or higher) of precious RAM.


Btw, my a570 has almost 100000 shots in its counter, and it's been powered on for about 3 days continuously. You would be switching cards and rebooting periodically, which helps a lot in avoiding odd bugs.
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Offline peabody

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Re: Time lapse feasibility
« Reply #6 on: 05 / April / 2009, 17:15:50 »
Canon makes AC adaptors for their cameras, and you can get generic equivalents for about half price on Ebay, etc.  But if you're going to be out and about, you would need to buy or build a power supply that draws off some larger battery source, like a car battery, or external pack of D cells or whatever.  And you would need the right connector for the power jack on the camera.  Or, of course you could just replace the regular batteries every few hours.

In one of my tests, the camera did ultimately shut down while the script was running.  It retracted the lens and shut down in the normal manner when the batteries got too low.  No apparent harm to the camera or the SD card.

The A590 has 640x480, but the next one up is 1600x1200.  Other models may have choices in between.

I think Fudgey may be right about there being a limit to how many exposures these cameras can really deal with at one time.  After one of my timelapse tests, I powered up the camera in playback mode when there were almost 3000 pictures on the SD card.  It just kinda sat there churning, presumably trying to set up a table of all the pictures on the card.  Anyway, it may make sense to use 4GB cards and replace them more often instead of a 16GB card.  And you would want to reset the filename counter too as he suggests.

If it's a critical session that you can't repeat, you definitely want to do a full test run with the camera, batteries, memory cards, etc., to make sure it's going to work.  This is particularly true if you will be using continuous power and very large SD cards.

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Offline jcarruthers

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Re: Time lapse feasibility
« Reply #7 on: 05 / April / 2009, 17:28:41 »
Yeah - it's pretty unrepeatable - we will be driving for 4 days around Europe - almost non-stop.

I'm wondering if a decent webcam will be a better option now... at least it might be a bit more reliable... hmm...

Thanks for all your replies everyone.
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Offline fudgey

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Re: Time lapse feasibility
« Reply #8 on: 06 / April / 2009, 14:20:20 »
Quote from: peabody on 05 / April / 2009, 17:15:50
After one of my timelapse tests, I powered up the camera in playback mode when there were almost 3000 pictures on the SD card.  It just kinda sat there churning, presumably trying to set up a table of all the pictures on the card. 

Yea, been there done that. I even once filled two DCIM directories with jpegs (i.e. 20000 in total...) to see if the camera can handle it...turns out it can, but it takes a whole lot of time... I think booting to play mode took about 15 seconds with a reasonably fast SDHC card. If I remember correctly, booting directly to REC mode was a better idea in this case. But I don't remember when if it started building those tables in background or after first shot or once first switching to PLAY mode.

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Offline peabody

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Re: Time lapse feasibility
« Reply #9 on: 06 / April / 2009, 19:26:24 »
Quote from: jcarruthers on 05 / April / 2009, 17:28:41
Yeah - it's pretty unrepeatable - we will be driving for 4 days around Europe - almost non-stop.

I'm wondering if a decent webcam will be a better option now... at least it might be a bit more reliable... hmm...

Thanks for all your replies everyone.

Well, with a webcam you have to worry about keeping your laptop powered up the whole time.

It would be nice if they made camcorders with an intervalometer function built-in.  But I've never seen one like that.   But that's how time lapses were done in the days of film - a movie camera that could be slowed way down.

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