The input gif had 108900 frames, all either yellow or green. By mapping each one to a single white or black pixel of an image, we can get to a qr code.
The tricky part here was that the frame data was identical for each one of them, while the thing to change was the first entry in the color palette, effectively modifying the color without touching the actual pixel data.
[Full writeup at https://theromanxpl0it.github.io/ctf_3ds2017/2017/12/20/microscope.html](https://theromanxpl0it.github.io/ctf_3ds2017/2017/12/20/microscope.html)