Monday, November 2, 2009

Time-lapse Sunset

I think I've mentioned before that the back of our house has a great view of the sunset. The house sits on a bit of a hill, so the back end is raised pretty high off the ground, and we have a relatively clear view out to the west. Whenever I see a great sunset in the making out our back door (and they seem to happen pretty often around here), I tend to bemoan the fact that I can't be out somewhere interesting shooting it.

I've found a bit of a solution to that, though. The view isn't quite spectacular enough to make a single photo workable, but I think making a time lapse video can add just enough interest to it to make it fun.

Time-lapse Sunset, October 24, 2009 from Chris McCormick on Vimeo.

Technically, this isn't the first time I've done this. I shot another one of these over a year ago, but never really finished pulling the video together. I've learned a lot from these two attempts, and I think there are some good things that I can do to improve it for next time around.

Here's what I did to create this.

Taking the pictures
The video is composed of 159 shots each taken 10 seconds apart.

To take the shots, I setup the camera on the tripod, and hooked it up to our laptop.

Our Canon 20D came with some software called "EOS Capture" for basically controlling the camera from the laptop (for my own reference, you launch the "EOS Viewer Utility", then find EOS capture in the menu). One of the features is a sort of "intervalometer" which allows you to program it to take a certain number of shots with a certain spacing. I set it up to to take 180 shots at 10 second intervals, giving me 30 minutes. The camera battery wasn't fully charged, though, and it stopped shooting after 159. It's a bummer--you can tell from the video that there was still plenty of color left in the sky when it stopped!

As for the camera settings, I left it on aperture priority mode with an fstop of f/5.6. The lighting obviously changes as the sun goes down, so you need to use one of the camera's auto-exposure modes so that it adjusts. I chose aperture priority because I wanted to make sure that the depth of field stayed constant the whole time.

One thing I forgot about, though, was the white balance. I left it on auto white balance, which probably accounts for some of the shifts in color between different frames. Ideally, I think you'd want to have the same white balance the whole time.

I almost always shoot in RAW format, and with RAW you can go back and set the white balance after the fact. This time, though, I shot JPEG thinking that would save me a step, since the video software would likely need JPEGs. Oops!

Next time, I think I'll leave it on auto white balance, but shoot in RAW, and then go back afterward to apply the same color temperature to all of the shots.

Editing the shots
Yet another opportunity for me to rave about the merits of Adobe's Lightroom. It makes batch editing incredibly easy. You just select one of the photos, perform all of the edits you want to make--color, cropping, and all of that--then just copy those changes to all of the other photos. You select the photo you edited, click "Copy settings...", choose which types of edits you want to copy, select all of the other photos, and click "Paste settings". And that's it, it batch edits all of your photos for you. Sweet!

Knowing that this wasn't going to be much of a masterpiece, I edited the photos pretty hastily. I boosted the contrast and saturation, played with curves a bit to add more contrast to the sky, and cropped it into a 16:9 aspect ratio for HD video.

Creating the video
I was able to pull together the video in iMovie. I haven't used iMovie before, so it took me a while to figure out how to set the spacing between the jpegs. A couple notes for my own reference:
- Once the jpegs are ready, import the photos into iPhoto first, then from iPhoto to iMovie. If you go straight to iMovie, the order of the photos gets mixed up
- Set the frame rate by selecting the images and clicking the 'Inspector' button. Go to "Clip" settings and set the duration of the images.

iMovie would only let me go as high as 10 frames per second, but videos typically run at 30fps. I found that there's a powerful UNIX-based command line tool called ffmpeg which you can use to create these videos. Next time around, if my shots are looking more promising, I think I might put the effort in to using that tool to get a smoother video. The speed of the cloud movement was pretty good, so to balance out the increased framerate, I would try taking the pictures 5 seconds apart instead of 10.


  1. This may be an old post, but it's helped me out. Thanks.