To connect two microphones to a single camera, you'll need a cable that will combine two audio outputs into a single input. The RØDE SC11 is perfect. This is a high-quality TRS Y-splitter cable for connecting two mono 3.5mm outputs to a single stereo 3.5mm input, like the one on your camera.
What happens when you have multiple mics on one source?
Phase becomes a problem when multiple microphones record a single source, and the sound reaches each mic capsule at a slightly different time — the combination of slightly out of time mic signals results in cancellations and reinforcements that change the tonality of the recording.
Can I split a microphone input?
Microphones can usually be split to up to three, and in some cases even four, destinations without the use of electronics. The number of splits that can be accomplished depends on the application, impedances present in the system, length of the cables and the quality of the components used in the splitter.