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 Panasonic FH20 and Olympus E-PL1 side-by-side from the front, back and top in their relative dimensions. Panasonic FH20 has external dimensions of 100 x 56 x 28 mm (3.94 x 2.2 x 1.1″) and weighs 178 g (0.39 lb / 6.28 oz) (including batteries). Olympus E-PL1 has external dimensions of 115 x 72 x 42 mm (4.53 x 2.83 x 1.65″) and weighs 334 g (0.74 lb / 11.78 oz) (including batteries).
Below you can see the front-view size comparison of the Panasonic FH20 and the Olympus E-PL1. Panasonic FH20 is clearly the smaller of the two cameras. Its body is 15mm narrower, 16mm shorter and 14mm thinner than Olympus E-PL1. As you can tell, actually this is not a fair size comparison since Panasonic FH20 has a built-in lens but Olympus E-PL1 doesn't. Once you put a lens on E-PL1, its thickness will increase significantly.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Panasonic FH20 is significantly lighter (156g ) than the Olympus E-PL1 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-PL1, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Panasonic Lumix DMC-FH20 (Lumix DMC-FS30) nor Olympus PEN E-PL1 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 Compact Cameras with Weather Sealing Top Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Panasonic FH20 and Olympus E-PL1's LCD screens have the same diagonal size of 2.70 inches.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.