Rotoscoping in After Effects

Recently I rotoscope these two horses running diagonally across the frame into camera, shot on a wide angled lense they went from 8 pixels high to filing the screen. not all that much fun. I was lucky, the footage was shot at 100 fps because they were being re-timed later. I used some useful tips from Mark Christiansen's book on studio techniques; such as using multiple mask instead of one horribly complex beast of a mask, starting simple adding points as you need them and keying where possible (the sky was very blue). I also found that with the reddish horses on a green and blue background I was able to duplicate the footage, desaturate the bottom layer then applying the masks to the top layer. This helped to find the edge of a horse by looking for the correct colour pixels, which was handy when zoomed in closely to the footage. Also I recommend making sure cycle mask colours is ticked in your display preferences.
 

then all you need is a quiet room and lots of patience.

-Jason