Large Four Thirds (17.3 x 13 mm) sensor
Large sensors provide shallower depth of field and a nice blurry background for your portrait shots. Image Stabilization
Image stabilization reduces the effects of camera shake at long exposures and long focal lengths thus ensuring sharper portraits
Average Resolution Sensor: 12.0MP
Olympus E-P1's 12.0MP resolution is not the best in its class but you can still manage relatively large prints of your portrait shots and crop without losing too much detail. Average Ergonomics&Handling
Good handling and existence of well placed physical controls on the camera body is very important during portrait shooting. It is faster and more intuitive to change the camera settings with dedicated buttons and knobs instead delving into the menus on the LCD.
No Built-in Viewfinder
In the lack of a a viewfinder, holding the camera away from the body while using live view is not very stable, especial with heavy camera bodies and lenses. Besides, LCD screens are very hard to read under bright sunlight.