Size and weight is a big decision factor when you are trying to find the ideal camera for your needs.
In this section, We are going to illustrate Nikon P500 and Olympus E-P3 side-by-side from the front, back and top in their relative dimensions. Nikon P500 has external dimensions of 116 x 84 x 10 mm (4.57 x 3.31 x 4.06″) and weighs 494 g (1.09 lb / 17.43 oz) (including batteries). Olympus E-P3 has external dimensions of 122 x 69 x 34 mm (4.8 x 2.72 x 1.34″) and weighs 369 g (0.81 lb / 13.02 oz) (including batteries).
Below you can see the front view size comparison of Nikon P500 and Olympus E-P3. Olympus E-P3 is 15mm shorter and 69mm thinner than Nikon P500 but it is also 6mm wider. As you can tell, actually this is not a fair size comparison since Nikon P500 has a built-in lens but Olympus E-P3 doesn't. Once you put a lens on E-P3, its thickness will increase significantly.
Here is the back view size comparison of Nikon P500 and Olympus E-P3.
Now lets look at the top view comparison of Nikon P500 and Olympus E-P3.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Olympus E-P3 is significantly lighter (125g ) than the Nikon P500 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-P3, the total kit will weigh much higher.
Unfortunately neither Nikon Coolpix P500 nor Olympus PEN E-P3 provides any type of weather sealing in their body, 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
Nikon P500 and Olympus E-P3's LCD screens has the same diagonal size of 3".
On the other hand, Nikon P500 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 Olympus E-P3 has a fixed type screen which provides less flexibility in shooting positions compared to P500.