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-   -   Time Lapse of a Freeway (https://www.dvinfo.net/forum/canon-xl-gl-series-dv-camcorders/90959-time-lapse-freeway.html)

Matt Newcomb April 7th, 2007 03:55 PM

Time Lapse of a Freeway
My office overlooks the 405 freeway and I want to get a time lapse of the traffic. I was wondering what kinds of settings I would maybe want to use for something like this. I know there are different frequencies and lengths of clips I can take but it just seems like there would be huge jumps with any fast moving stuff.

Also I'd like to get a day to night transition, and was wondering how you can get a decent exposure on something like that.

John Miller April 7th, 2007 07:07 PM

The first thing to do is determine the time lapse rate. i.e., record one frame every n frames.

Let's say the day-to-night transition takes 60 minutes in real time and you want to condense it to a clip that lasts 15 seconds. You need to record one frame every (60 * 60 / 15) frames = 240 frames.

If the real time event lasts less that the duration of a single tape, I would record the event on to a miniDV tape. Then do the following:

Assuming you can hook up your camcorder via FireWire to a PC, use a DV capturing tool that can do time lapse. Our Enosoft DV Processor can do that (you need Windows XP or later and a CPU with SSE2 instructions) and I believe WinDV can, too. Simply tell the software to capture one frame every 240 frames (from the above calculation) and you'll end up with a DV file that, when played back, will show the whole event greatly speeded up.

If you don't know quite what speed to want, the alternative process is to use our software to capture the whole event in real time (either live or from tape) and then perform time lapse on the captured file. This way you can try different rates without having to re-capture or re-record.

I know some camcorders have a time lapse function but I would be wary of using such a feature because of the possible wear-and-tear of having the heads running all the time while the tape is advanced intermittently.

Jacob Ehrichs April 7th, 2007 07:43 PM

Another option if it's longer than 90 minutes for an LP tape is to go directly to your computer and bypass the tape all together. Couple factors go into that obviously, you need to be able to power a computer and your camera for the duration and have the software that is capable of capturing at different frame rates than the standard.

I did this with:
XL1 - AC powered
Laptop with firewire card - AC powered
Premiere 6.0 (has a stop motion feature that has been removed in the Pro version)

Anthony Park April 8th, 2007 06:46 PM

I used my XL2 on a project where about 20 men where building a playground including earthworks and assembly of playground equipment and fencing that took about 6 hrs to complete. I set the camera on my tripod before they started, used Av setting to allow for different light changes through the day and set the interval timer to record a 1.5 sec clip every 30secs. I then had to reduce this to a 20 sec clip in my NLE which turned out great. It was funny seeing the project go from nothing to a full blown playground with the sky changing colours and machinery moving so quickly. I had the camera under a awning in case it rained and connected the camera to a powerpoint with a sign that I wrote saying DO NOT PULL OUT(complete with scull & crossbones picture)

David Lach April 9th, 2007 03:38 PM

Best way to get really smooth time lapses involves, as John mentioned, the recording of single frames per x amount of time, as opposed to sequences of frames per x amount of time. The XL2 cannot do such a thing as single frame recording since it is a tape based recording system, so it has to record sequences (multiple frames, valued in seconds) which depending on the wanted effect, will give a juddery and irregular look to the final time lapse. So if you can manage with a 60 minute recording, use a tape and speed up in post. If not, use a computer or similar device recording to pass the 60 min. time limit.

For your question regarding exposure, there are a couple ways to do this. If the city lights are strong enough to get decent exposure at night, at an opening close to your starting exposure, you could choose a fixed exposure setting (might require prior testing) and compensate in post in a linear manner for any faint light variations (brighten up the image as the sun comes down).

But chances are though that you will need aperture readjustment during the shoot. I've used the auto iris mode on the XL2 with good results (with a -1 exposure compensation to avoid white clipping and fixed shutter speed), but this will be dependent on your framing and how the lighting changes inside the frame. Things that could cause irregular exposure changes in auto mode are mostly clouds, but also anything else that will affect the ambiant light outside of the sun coming down. Again, frame accordingly.

You might want to experiment with the shutter speed too. A low shutter speed effect (like 1/15th) will provide for some added motion blur, which tend to give a nice look on fast moving car lights (personal taste of course, again, experiment).

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