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I am shooting a time lapse and am doing some calculations beforehand to make sure I get everything right.

I am shooting a road trip from the west coast to the east coast and am planning to compress it down to about 4 minutes or 5760 frames at 24 fps (I was originally planning 30 fps, but blu ray is 24 fps).

I am reading various articles online and have shot a few time-lapse sample videos myself. The first video I shot recorded pictures at 1 frame / second with a variable shutter speed of 1/60 or faster. The second shot at 1/3.5 second every 10 seconds.

I stitched both into videos at a frame rate of 30 fps, the one shot at 1/3.5 second is much smoother than the one shot at 1/60 second or faster.

reference: http://en.wikipedia.org/wiki/Time-lapse

My questions:

  1. What should my exposure time be if I take a picture every 10 seconds?
  2. Should it be 5 seconds?
  3. Should I take more pictures than 5760 over the entire length of the trip?

I was thinking that I would shoot more than 5760 frames so that I have more pictures to choose from so the picture would be smoother. Alternatively, I was thinking I could do a longer exposure to make up for the lack of total frames I would have.

It looks like I will have to use my DSLR as I can't find an inexpensive point and shoot that I feel comfortable using. I have looked at a JVC GC-WP10 (online), but I don't feel I would have enough control over the camera.

Thanks,

Walter

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1  
Have you experimented with a short trip? A sequence of photos taken from a moving, vibrating platform at 1/2 - 1 mile intervals is going to be unviewable if replayed at standard video speed. Good slide show, maybe. –  whuber Jan 13 '11 at 16:16
    
I experimented with a drive around the block at 25 - 35 mph (210 seconds in 7 seconds). I shot at 1 fps (when the camera could keep up). It looked relatively smooth when played back at 30 fps. –  Walter White Jan 13 '11 at 18:25
    
I was thinking about using my phone to take pictures. It has 32 GB storage plus an external 16 GB card. I can charge it when we're driving, download pictures wirelessly through an ad-hoc wireless network via ssh, and programmatically control the camera through scripts. The only problem I have now with that is, finding a good mount for the n900. –  Walter White Jan 13 '11 at 20:26
    
@Walter 1 fps at 30 mph = one frame every 44 feet, not one frame every 5280 feet (one mile). One mile = two minutes at these speeds. What do you think of the result when you select one frame for every two minutes? –  whuber Jan 13 '11 at 21:16
1  
You probably won't want to manually sort through and select photos; instead, you'd take every 2 or 3 photos using a script, or maybe blend photos together if you have CPU cycles to waste. –  Evan Krall Jan 14 '11 at 5:17

4 Answers 4

As of question 2 - Your interval should be 10 sec. Your exposure time should be whatever is the meter reading for correct exposure (5 secs will get you overly exposed frames).

For 4 minutes video, you calculation of 5760 frames at 24 fps is correct. However this will get you 57,600 seconds (@ 10 sec per frame) which are less than 1 day. I don't see how you can conclude the trip in this time.

The right calculation is to take the length of the trip (say, 10 days = 864,000 secs) and divide by the # of frames (5760) to get the interval between frames (around 2 minutes in this case).

You may want to shoot in shorter interval and take more pictures so that you can make longer movie or have different fps.

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OK, I've never tried this but my intuition is that this makes no sense. Unless you are driving straight for 10 days and not sleeping or eating except at the wheel, you're going to need a lot more frames and then edit it down to 4 mins. –  Itai Jan 13 '11 at 16:28
    
@Itai - the OP doesn't say if he shoots his time lapse only for specific periods every day. If so, of course the calculations need to be corrected accordingly - that is, decide how much time per day the camera is active (in seconds) and replace the 84600 figure with that number. So, for 1/2 day shoot, it would be 10x42300 = 423000 secs -> 423000/5760 = 73 sec or approx. 1 minute between captures. –  ysap Jan 13 '11 at 16:35
    
I was going to shoot around the clock, at night, I was planning to lower the rate at which I take pictures to 1/10 of the day rate. I will also probably cut out boring stuff such as stopping for gas. –  Walter White Jan 13 '11 at 18:24
    
I realize a 5 second exposure is long during the day, probably still outside of what a polarizer can bring down and a really small aperture. –  Walter White Jan 13 '11 at 18:27
    
@Walter White - even if it was within the polarizer/aperture capability, why would you want to expose for 5 seconds in the first place? BTW, if you insist, a strong ND (Neutral Density) filter is more adequate than a polarizer here. –  ysap Jan 13 '11 at 18:35

"What should my exposure time be if I take a picture every 10 seconds?"

Your exposure time should be 'whatever it needs to be' in order to get as close to the 'proper' picture exposure for the environment you're in as possible. In practice this will be impossible to get completely correct (without the use of an external homebrew realtime light meter and intervalometer... which is what I use. Shoot me a message if you're a DIY electronics guy who is up for building your own equipment and I'd be happy to point you to some excellent resources...), because the light will be changing constantly throughout your trip, but you can set it so that the fluctuations aren't too extreme, and then adjust it throughout the day/trip as the lighting changes, paying special attention to dawn and dusk hours (or simply not taking pictures during those times of especially rapid light change).

"Should it be 5 seconds?"

Possibly for shooting at night, but 5 seconds will almost certainly be way too long of an exposure for shooting during the day. Again, the specific choice of exposure time needs to be dictated by the actual conditions you're in when you're shooting the timelapse... Any answer to this question given here will be pure speculation at best.

"Should I take more pictures than 5760 over the entire length of the trip?"

Given the variables that you've provided...

Yes. If you can take more pictures, you almost certainly should take more pictures. My recommendation is to take as many pictures as you possibly can. In other words, work in manual mode, set your shutter, f-stop and iso, then simply have your intervalometer fire frames as fast as your camera can go.

The reason for this is that it is extremely easy to speed your timelapse up (by simply removing a given number of frames in post) if you need to, but it is nearly impossible to slow a timelapse down in post (because there are no extra frames to add).

Now this assumes that:

  • You don't care about shutter actuations (And you shouldn't. Folks who worry about that are almost always being penny-wise and pound foolish with a part of their camera that can be replaced for about $200... Depending on the shutters expected total number of actuations this is between .004 cents and .00006 cents per actuation. Cheap!)
  • You have enough storage space (External large terabite drives can be purchased for under $100... This shouldn't be an issue)
  • You are in a position where you can dump your frames directly to your computer in realtime as the trip unfolds (Because you probably don't want to be frequently stopping in order to dump cards to your computer)

If the above assumptions aren't true, then it becomes very easy to calculate for the total number of actuations that you want to 'spend,' and/or your total amount of HD space, and/or the number of times you want to stop to 'manage' your cards.

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The first thing you need to figure into your calculation is total length of time your trip is going to take. I don't see that so forgive me if I missed it. If you're hauling butt and make the trip in 20 hours then you have 86400 seconds of driving time. At ten second intervals this would give you 8640 exposures which equals 6 mins of footage (1 frame=1 exposure).

*special note I like your decision to go with 24/fps, looks better.

Whether or not you have 4 mins or 6 or even 12 isn't the real issue though. You can adjust the overall speed of your TL once compiled. Of greater note is logistics.

To answer your question:

  1. Exposure time, under ten seconds, should be appropriate to correct exposure and aesthetic. Unless you are shooting at a very high speed, shutter drag will be apparent. Personally I think drag would look better in this case. It will enhance the sense of motion. I did something like that in the opening sequence here.

  2. Same as above. This is a personal choice. The actually length of the exposure will not effect the overall length of the TL. Of greater consequence is the processing speed of your camera. Can it handle a 5 sec exposure every ten seconds without filling its buffer? My D100 can not, though my D700 can.

  3. Personally I would. Even with shutter drag, a 10 sec gap "may" be too much for the eye. In other words, you run the risk of creating a choppy experience. I would do a quick test on your local highway at cruising speed and see how it turns out. When I TL clouds, I shoot every sec or two to minimize that gap. Certainly the prospective on clouds will be relatively slower than scenery on a highway.

Hope that answers some of your questions. Now here's a few other things to consider (from experience):

-Power Supply; how are you powering your camera throughout the trip. That continuos draw on battery from shutter and processor will kill them off quick. Make sure you're plugged into your A/C adapter.

-Mounting; your camera has to be firmly locked into the vehicle. The smallest bump (pulling into a gas station for example) can knock your camera off axis and then the whole last leg of the trip is for not. A bump of the camera, even the smallest one, is TL no-no. Also, you have to be able to move around your camera without bumping it. So make sure you have room to grab your munchies before your start your journey.

-At night; now that you have your mount squared away, what to do with your camera when you sleep. Nothing would be worse then to wake up to a broken window and stolen gear (again from experience). They are out there and they will steal your rig. Make sure your mount is secure enough that you can remove your rig in a way that allows you to precisely maintain your composition.

Good luck and happy hunting. I'd love to see your finished product.

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I was planning to mount the camera in the rear window looking forward or possibly the right rear window looking forward. I was thinking about putting up tint in the rear windows to hide the camera. Do you think that would be adequate to 'hide' it. Reminds me of the Jerry Seinfeld comment, putting sweaters over a tv, it's just a couple of sweaters with an antenna sticking out ... –  Walter White Jan 13 '11 at 20:20
    
Nice Seinfeld reference. I like that idea. Wonder if you could hang a blanket in front of it at night or something. Definitely park with the rear of your car closest to your door. Or perhaps right by the front desk so you have eyes on it all night. –  Rob Clement Jan 13 '11 at 21:03
    
Come to think of it, if you parked so the camera was pointing at the hotel lobby/sign, and you stayed at the same hotel chain the entire time, you might be able to sell the time lapse to that hotel. Just a thought. –  Rob Clement Jan 13 '11 at 21:56
    
I am planning to stay at bed and breakfasts for most of the trip. –  Walter White Jan 13 '11 at 23:45
    
@Rob Clement - your tips are all meaningful, this is why I am leaning towards using my n900. I can plug it into the car while driving (via USB / cigarette adapter) so I have power. Secondly, it has 48 GB of storage locally, and I can dump pictures while driving to my laptop via wireless (if I use USB, it will unmount the filesystem, so I won't be able to save pictures while it is mounted ...). So, the real problem at that point becomes, I don't have a good mount for the n900 nor a good time lapse application for it. –  Walter White Jan 13 '11 at 23:49

About mounting the camera, how about something like this:

http://www.ram-mount.com/NewProducts/cellphonemount/tabid/3436/Default.aspx

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That is a good suggestion - instead of mounting it with the screen out, I would mount it with the screen in. I can then take pictures with it. It doesn't look very sturdy from the pictures though –  Walter White Jan 14 '11 at 13:31

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