May 11, 2008
News - Enginursday: Time-lapse w…
about a year ago
I think you’d actually want to do the opposite with regards to the shutter speed - slow it down to be much slower than the frequency of the light. That way, you’re averaging out the exposure through multiple on/off cycles of the light. I’d suggest using as high of an f-stop (smallest aperature) possible on your camera, then adjust the exposure time to be as long as possible without overexposure. If the set up is still too bright you could throw a neutral density filter in front of the lens.
As a generic, cross-platform answer I’d recommend either ImageJ or Fiji. ImageJ is a free technical image processing program made by the NIH that runs on Windows, OSX, or Linux (it’s Java-based).
Fiji,which stands for “Fiji Is Just ImageJ”, is a repackaging of ImageJ with some extra fancy plugins, mostly geared towards microscopy.
I’ve tried a couple of different methods for processing still images into movies, and ImageJ is by far the easiest way I’ve found to get high-quality video files that are small in file size and run on every computer I’ve tried them on (other methods I’ve tried had way too much wrestling with codecs). A simple way to get started with time lapse in ImageJ is to import a sequence of images (super easy if your images are named sequentially), then just Save As an AVI with JPEG encoding. You can specify the frame rate in the Save As dialog.
There are lots of handy plugins for ImageJ, and Fiji includes one that is super-handy for time lapses if your mount is not rock-solid: it’s an image registration plugin called StackReg. If your camera moves a little bit during image acquisition, the resulting video will look jittery. StackReg will step through your image sequence, and try to match up each image with the one before it. As long as you don’t have drastic changes between frames it should do a good job of eliminating the jitter.
Note, the above directions I gave will work in either ImageJ or Fiji. Fiji might be the better choice for getting started - I know it is actively developed and updated, while I believe the ImageJ developers are hard at work on a version 2 so there is consequently less work being done on the current version.
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