I have begun testing different microphones with my 5D. I have a sony condenser mic that my dad bought in the 80's and i have found that it has the best sound quality compared to my other mics. The sony condenser has a 1/4 inch mono plug and I am using a mono 1/4in to 1/8in converter to plug into the 5D'd mic jack. My problem is when i play back the video on my computer I only get sound out of my left speaker. When i check the audio in soundtrack sure enough the left channel is the only track that has audio data.

Would using a stereo 1/4in to 1/8in converter instead of a mono one fix this?

Any camera settings to correct this?

Do I have to correct this in post production if i want to use my sony condenser?

Any advice would be appreciated.

Q. Would using a stereo 1/4in to 1/8in converter instead of a mono one fix this?

A. Depending on the adapters layout, it should. Radio Shack is the place to go in and test it with various.

Q. Any camera settings to correct this?

A. No

Q. Do I have to correct this in post production if i want to use my sony condenser?

A. Not necessarily. You can get various adapters that will output a mono signal to two channel. However, it is just a simple to have you NLE output to both tracks. It is a simple process in Vegas, for instance.

thankyou for your input, i if i cant find my stereo converter i got a radioshack down the street from me.

RadioShack actually has a 1/8" mono to 1/8" stereo adapter that I had to use for years with my old camera and mic. I have never seen a 1/4" to 1/8" adapter that also did the mono to stereo adaptation. You can't just use any adapter, you need one that is wired specifically to route the mono signal to both stereo channels.

It is a simple process in Vegas, for instance.

Right-click > Channels > Left Channel Only

I love Vegas... :)

or maybe consider buying a Rode Videomic? They are cheap (but good) and have a plug type on them which should feed mono sound onto both channels (assuming the mic input plug on the 5DMkII is the same size as on my 7D - I imagine it is) or just do it all in post as indicated above. The Rode VM will give you better sound anyway - I suspect - so consider it.

Dual system/off camera sound would be even better ....but one step at a time!

Why not just convert the single channel to mono in post? This is usually a quick adjustment in most NLEs.

These are all good suggestions. For the moment I'd go with using your NLE to route the output to both Left and Right.

Quickly searching doesn't reveal a single adapter that does what you want; to go from mono 1/4" female to stereo 1/8" male.
However you can either wire up your own or combine two adapters, like these two:
Neutrik NYS236 1/4 Inch Mono Jack to 1/4 Inch Mono Jack Coupler at AmericanMusical.com (http://www.americanmusical.com/Item--i-NEU-NYS236)
and
Hosa CMP100 Series 1/8 Inch TRS to 1/4 Inch TS Cable at AmericanMusical.com (http://www.americanmusical.com/Item--i-HOS-CMP110-LIST)
This combo of inline coupler and adapter cable would send the audio from your mono mic into both channels of the stereo mic jack.
In addition it would take some strain off your 1/8" mic input jack because the cable would connect there and the heavier adapters would be at the other end of the cable allowing you to secure the lighter cable end more easily.