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 Pentax K-5 IIs and Fujifilm X100S side-by-side from the front, back and top in their relative dimensions. Pentax K-5 IIs has external dimensions of 131 x 97 x 73 mm (5.16 x 3.82 x 2.87″) and weighs 760 g (1.68 lb / 26.81 oz) (including batteries). Fujifilm X100S has external dimensions of 127 x 74 x 54 mm (5 x 2.91 x 2.13″) and weighs 445 g (0.98 lb / 15.70 oz) (including batteries).
Below you can see the front-view size comparison of the Pentax K-5 IIs and the Fujifilm X100S. Fujifilm X100S is clearly the smaller of the two cameras. Its body is 4mm narrower, 23mm shorter and 19mm thinner than Pentax K-5 IIs. As you can tell, actually this is not a fair size comparison since Fujifilm X100S has a built-in lens but Pentax K-5 IIs doesn't. Once you put a lens on K-5 IIs, its thickness will increase significantly.
Now lets look at the top view comparison of Pentax K-5 IIs and Fujifilm X100S.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Fujifilm X100S is significantly lighter (315g ) than the Pentax K-5 IIs 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 K-5 IIs, the total kit will weigh much higher.
Weather Sealing
With its weather-sealed body, we believe that the K-5 IIs has a big advantage over the X100S which doesn't provide any kind of environmental sealing.
LCD Screen Size and Features
Pentax K-5 IIs's 3.00" LCD screen is slightly larger than Fujifilm X100S's 2.8 screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.