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-PM1 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-PM1 has external dimensions of 110 x 64 x 34 mm (4.33 x 2.52 x 1.34″) and weighs 265 g (0.58 lb / 9.35 oz) (including batteries).
Below you can see the front view size comparison of Nikon P500 and Olympus E-PM1. Olympus E-PM1 is clearly the smaller of the two cameras. Its body is 6mm narrower, 20mm shorter and 69mm thinner than Nikon P500. As you can tell, actually this is not a fair size comparison since Nikon P500 has a built-in lens but Olympus E-PM1 doesn't. Once you put a lens on E-PM1, its thickness will increase significantly.
Here is the back view size comparison of Nikon P500 and Olympus E-PM1.
Now lets look at the top view comparison of Nikon P500 and Olympus E-PM1.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Olympus E-PM1 is significantly lighter (229g ) 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-PM1, the total kit will weigh much higher.
Unfortunately neither Nikon Coolpix P500 nor Olympus PEN E-PM1 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-PM1's LCD screens has the same diagonal size of 3.00".
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-PM1 has a fixed type screen which provides less flexibility in shooting positions compared to P500.