1 SD Card (small, just to hold the firmware).
They develop and test firmware for Canon cameras to liberate cameras to their full potential! Rather than recording to a codec that compresses video and reduces sharpness and image quality, users can install the ML firmware and not only shoot in raw, uncompressed video, but can see zebras, advanced audio levels, histograms, and much more. For years, I've been curious about the folks at Magic Lantern.