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 Olympus E-PL9 and Pentax Q-S1 side-by-side from the front, back and top in their relative dimensions. Olympus E-PL9 has external dimensions of 117 x 68 x 39 mm (4.61 x 2.68 x 1.54″) and weighs 380 g (0.84 lb / 13.40 oz) (including batteries). Pentax Q-S1 has external dimensions of 105 x 58 x 34 mm (4.13 x 2.28 x 1.34″) and weighs 203 g (0.45 lb / 7.16 oz) (including batteries).
Below you can see the front view size comparison of Olympus E-PL9 and Pentax Q-S1. Pentax Q-S1 is clearly the smaller of the two cameras. Its body is 12mm narrower, 10mm shorter and 5mm thinner than Olympus E-PL9.
Here is the back view size comparison of Olympus E-PL9 and Pentax Q-S1.
Now lets look at the top view comparison of Olympus E-PL9 and Pentax Q-S1.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Pentax Q-S1 is significantly lighter (177g ) than the Olympus E-PL9 which may become a big advantage especially on long walking trips.
Also keep in mind that body weight is not the only deciding factor when comparing two interchangeable camera bodies, you have to also take into account the lenses that you will be using with these bodies.
Unfortunately neither Olympus PEN E-PL9 nor Pentax Q-S1 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 Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Olympus E-PL9 and Pentax Q-S1's LCD screens has the same diagonal size of 3.
On the other hand, Olympus E-PL9 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 Pentax Q-S1 has a fixed type screen which provides less flexibility in shooting positions compared to E-PL9.