Light Painting is Easy with the Olympus OM-D E-M5
I won't go into details here because I wrote about it twice last year. First using the Fujifilm X100, and later with the Olympus PEN E-PL1. I not only talk just a little about technique but point you to some great websites about it, too.
The beauty of using this technique with the OM-D is centered in two features known as Live Bulb and Live Time. (The settings for these two are found in Custom Menu E.) In a nutshell, these two functions tell the camera to periodically update the live view on the LCD monitor, allowing you to track the exposure in "almost" real time. Then when it looks right … you end it.
The menu settings allow you set the desired interval for the camera to update the live view, but keep in mind the number of updates is limited. So you need to space them out to make sure it will cover your needed exposure time. Also the higher the ISO, the lower the number of allowed updates.
My favorite of the two modes is Live Time for one simple reason. It lets you start the exposure with a simple press of the shutter button and then end it the same way. With Live Bulb, you must hold the shutter button down (or use a cable remote with locking ability) for the entire time.
Previously, getting a good exposure while light painting was a function of luck, experience, and trial and error. Now, with the Olympus OM-D E-M5, we have a tool that can greatly shorten the learning curve and help you get the best exposure the first time. :-)