4. Shoot the Movie

Do the math to find out how long to wait between exposures—we shot the stars every 72 seconds.

Pick an interval between each frame that suits the subject. To condense about 10 minutes of photos into a several-second video, we often shoot one frame every 20 seconds. But you can estimate the interval by dividing the number of needed frames by the length of the event. For a 15-frames-per-second video, we might want a 10-second shot watching stars track across the sky (15 frames x 10 seconds = 150 frames). Since the real-time event takes about three hours, that’s 10,800 seconds (3 hours x 60 minutes x 60 seconds). That leaves 72 seconds between each shot (10,800 seconds/150 frames). You will no doubt need to experiment to find the best interval for your intended results.

It’s up to you to manually shoot each frame, although some cameras include a time-lapse timer to keep snapping after a set interval. Some cameras are also compatible with time-lapse shutter remotes that do the same thing. If you have neither, we still recommend using a “dumb” shutter remote that just snaps the picture so you can avoid touching the camera. But if it’s tightly anchored to the tripod and you touch it gently, you can still work without those extras. Eventually, you can gradually adjust zoom and framing as you shoot, but practice the basics by leaving the camera pointed in the same place.

5. Import the Photos

Using Image Capture will dump the individual images in a folder on your Mac, instead of adding them to the iPhoto library.

Connect the camera or memory card to your Mac, and open Image Capture (in your Applications folder). From the Download To pop-up menu, choose Other, and create a new folder for the photos. Download all of the images. Navigate to that folder and, if needed, erase any test photos taken before the time-lapse sequence. (Or instead, choose Download Some in Image Capture, and pick only the needed photos.)

6. Assemble the Video

Choose the first photo in your sequence here.

There are several ways that you can turn these images into a movie, but the easiest is with QuickTime Pro ($29.99, www.apple.com). This technique will also create a video file ready for any application.

Open QuickTime Player, and choose File > Open Image Sequence. Pick the first photo, then choose the frame rate. We think 15 frames per second works well. The new window will probably spill far outside your display. Pick View > Fit To Screen to tame the clip. If you play the movie now, you’ll get a rough idea of how it will look. Because the video is likely at an exceptionally high resolution, it’ll probably play at a choppy frame rate. Choose File > Save As to export the shot. Click the radio button to Save As A Self-Contained Movie. Depending on the speed of your system, this might take several minutes.

7. Edit

iMovie can import your clip as full HD, ready for editing.

Open iMovie, Final Cut Express, Final Cut Pro, or your favorite video editor to import the video. In iMovie, pick File > Import Movies. Select the clip, and be sure to import as 1920x1080 resolution. If you want, save disk space by clicking the radio button to Move Files Instead Of Making A Duplicate. Choose Import. Edit the clip, using the crop tool to adjust the framing if desired. Because of the big source file, the video will still play at a choppy rate until you finish and share the final project.