While Alex was in town for the weekend, we used my camera's intervalometer to record tracks in my gravel driveway. I'm still playing with the images, but I've got a pretty sweet sample uploaded to BoF Labs.
I set up the camera on a tripod and told it to take 1 image per minute for 7 minutes. The first image is useless because the tripod slowly settles over the course of the first minute. Between each pair of photos we made tracks in the camera's field of view.
- Pristine driveway
- This is the baseline image.
- Driveway with tracks
- I doubt you can see the footprints we made in the "after" photo, partly because the baseline image was already covered in tire, foot, and paw tracks.
- Difference between images
- I used the GIMP to subtract the former picture form the latter, which reveals the footprints as light areas in a sea of dark.
There was some tripod shift between other photo pairs, and I'm still working on aligning the photos. Already I'm thinking of other surfaces that might support before/after subtraction for tracking purposes. Carpet? Grass? Sand?