In 2006 I modified a Nikon MC-30 to accept input from an external source.This is an older post that I carried over from the old website.
I wanted to experiment with a sound trigger to take photographs of a balloon bursting. Someone borrowed me a homemade sound trigger, but the trigger was wired to an earphone jack type connector, which is not compatible with the round Nikon 9-pin plug. I could have tried to source a conversion cable to the Nikon 9-pin connector, but I had a MC-30 remote trigger and some time at hand.
The casing opened quite easily, but there is a nasty spring inside that I had to put carefully in position again when I re-assembled the parts. I drilled a hole in the side of the casing and I placed a short cable through the hole to an earphone jack socket. Thereafter, I could just plug the trigger into the earphone jack, and the MC30 provided the link to the camera. The MC-30 still functions as before.
The MC-30 white, violet and yellow wires trigger the camera. When the white and yellow wires are shorted the camera metering and focusing activate. When the white, violet and yellow wires are all shorted together the shutter is released. The yellow wire is ground, the white is SW1 (metering/AF) and the violet is SW2 (shutter release).
As they say on TV: “DO NOT TRY THIS AT HOME” – I had professional help and we spent quite some time testing first, to ensure we do not blow the camera’s electronics. Someone at Nikon was kind enough to check my MC-30 afterwards.
Here is a link to a similar project: http://www.whatartist.com/blog/2011/04/nikon-mc-30-shutter-release-hacked-for-remote-trigger-pocket-wizard/
I took these photos at that time. Since then, I shortened the cable to the earphone jack. It is perhaps even better to mount the earphone jack directly on the MC-30 casing. I have used this successfully for sound trigger photography, and with an infra-red beam for splash photography.
My (un)willing daughter in 2006 photographed using the sound trigger to get the balloon as it bursts. The microphone is visible in the image.