Size and weight are big decision factors when you are trying to find the ideal camera for your needs.
In this section, we are going to illustrate the Sony H400 and Olympus E-PM2 side-by-side from the front, back and top in their relative dimensions. Sony H400 has external dimensions of 130 x 95 x 122 mm (5.1 x 3.74 x 4.81″) and weighs 628 g (1.38 lb / 22.15 oz) (including batteries). Olympus E-PM2 has external dimensions of 110 x 64 x 34 mm (4.33 x 2.52 x 1.34″) and weighs 269 g (0.59 lb / 9.49 oz) (including batteries).
Below you can see the front-view size comparison of the Sony H400 and the Olympus E-PM2. Olympus E-PM2 is clearly the smaller of the two cameras. Its body is 20mm narrower, 31mm shorter and 88mm thinner than Sony H400. As you can tell, actually this is not a fair size comparison since Sony H400 has a built-in lens but Olympus E-PM2 doesn't. Once you put a lens on E-PM2, its thickness will increase significantly.
Now lets look at the top view comparison of Sony H400 and Olympus E-PM2.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Olympus E-PM2 is significantly lighter (359g ) than the Sony H400 which may become a big advantage especially on long walking trips.
Again, this comparison may not be very useful in real life as we are comparing the weight of a camera with a built-in lens to the body-only weight of an interchangeable lens camera. Once you put a lens on E-PM2, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Sony Cyber-shot DSC-H400 nor Olympus PEN E-PM2 provides any type of weather sealing in their bodies, so you have to give extra care especially when you are shooting outdoors. If weather sealing is a must-have feature for you, check these sections: Top Bridge Cameras with Weather Sealing Top Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Sony H400 and Olympus E-PM2's LCD screens have the same diagonal size of 3.00 inches.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.