Magic Lantern is a free software add-on that runs from the SD/CF card and adds a host of new features to Canon EOS cameras that weren't included from the factory by Canon.
I also found this concise, human-written readme on the project page. Since it's not AI slop churned out by a startup, it's worth reading! :-)))
Magic Lantern
=============
Magic Lantern (ML) is a software enhancement that offers increased
functionality to the excellent Canon DSLR cameras.
It's an open framework, licensed under GPL, for developing extensions to the
official firmware.
Magic Lantern is not a *hack*, or a modified firmware, **it is an
independent program that runs alongside Canon's own software**.
Each time you start your camera, Magic Lantern is loaded from your memory
card. Our only modification was to enable the ability to run software
from the memory card.
ML is being developed by photo and video enthusiasts, adding
functionality such as: HDR images and video, timelapse, motion
detection, focus assist tools, manual audio controls much more.
For more details on Magic Lantern please see [http://www.magiclantern.fm/](http://www.magiclantern.fm/)
There is a sibling repo for our patched version of Qemu that adds support
for emulating camera ROMs. This allows testing without access to a physical
camera, and automating tests across a suite of cameras.
https://github.com/reticulatedpines/qemu-eos
https://github.com/reticulatedpines/qemu-eos/tree/qemu-eos-v4.2.1 (current ML team supported branch)
https://github.com/reticulatedpines/magiclantern_simplified/...