Nikon DSLRs have a plus and minus to having their firmware hacked. The plus is that Nikon is one of the few things around where you can actually go back in firmware by installing an older version. The minus is that Nikon DSLRs can't execute outside of the camera firmware. That's what made the Canon Magic Lantern hacks so popular: you could install them on an SD card and there was no memory limit to how big the hack could be.
So Nikon DSLR hacks tend to be very simple. Many are just overrides to a function that already exists, while others are simply an implementation of something already in firmware that wasn't brought out to the user.
So what are we talking about here?
The EXPEED2 and EXPEED3 cameras seem to be the ones that have been worked on the most. That would be the D3100, D3200, D5100, D5200, D7000, D600, D610, D800/800E, and D4. Nikon made changes to firmware starting with EXPEED4 that, as far as I know, haven't yet been reverse engineered.
What kinds of things are supported with hacks?
- Using non-Nikon batteries
- Adding Manual ISO and shutter speed to Live View
- Clean video output on the HDMI port
- Uncropped video on the HDMI port
- Removal of video time limits
- Higher quality bitrate on video
- Optimal Quality JPEG
- Lossless NEF Compression
- Disabling the hot pixel suppression routine (star eater)
One of the best sources of the current state of Nikon DSLR hacks is Nikon Hacker. That page also includes reverse-engineered information about other things, including the lens mount and USB communications, as well as pointers to some useful utilities.
