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 Olympus E-PL3 and Nikon P310 side-by-side from the front, back and top in their relative dimensions. Olympus E-PL3 has external dimensions of 110 x 64 x 37 mm (4.33 x 2.52 x 1.46″) and weighs 313 g (0.69 lb / 11.04 oz) (including batteries). Nikon P310 has external dimensions of 103 x 58 x 32 mm (4.06 x 2.28 x 1.26″) and weighs 194 g (0.43 lb / 6.84 oz) (including batteries).
Below you can see the front-view size comparison of the Olympus E-PL3 and the Nikon P310. Nikon P310 is clearly the smaller of the two cameras. Its body is 7mm narrower, 6mm shorter and 5mm thinner than Olympus E-PL3. As you can tell, actually this is not a fair size comparison since Nikon P310 has a built-in lens but Olympus E-PL3 doesn't. Once you put a lens on E-PL3, its thickness will increase significantly.
Here is the back view size comparison of the Olympus E-PL3 and Nikon P310.
Now lets look at the top view comparison of Olympus E-PL3 and Nikon P310.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Nikon P310 is significantly lighter (119g ) than the Olympus E-PL3 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-PL3, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Olympus PEN E-PL3 nor Nikon Coolpix P310 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 Mirrorless Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Olympus E-PL3 and Nikon P310's LCD screens have the same diagonal size of 3.00 inches.
On the other hand, Olympus E-PL3 features a
Tilting screen where you can change the angle of the screen to make it easier to shoot from waist or over-the-head levels whereas the Nikon P310 has a fixed type screen which provides less flexibility in shooting positions compared to E-PL3.