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 Nikon D5100 and Fujifilm X100S side-by-side from the front, back and top in their relative dimensions. Nikon D5100 has external dimensions of 128 x 97 x 79 mm (5.04 x 3.82 x 3.11″) and weighs 560 g (1.23 lb / 19.75 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 Nikon D5100 and the Fujifilm X100S. Fujifilm X100S is clearly the smaller of the two cameras. Its body is 1mm narrower, 23mm shorter and 25mm thinner than Nikon D5100. As you can tell, actually this is not a fair size comparison since Fujifilm X100S has a built-in lens but Nikon D5100 doesn't. Once you put a lens on D5100, its thickness will increase significantly.
Here is the back view size comparison of the Nikon D5100 and Fujifilm X100S.
Now lets look at the top view comparison of Nikon D5100 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 (115g ) than the Nikon D5100 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 D5100, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Nikon D5100 nor Fujifilm X100S 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 DSLR Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Nikon D5100's 3.00" LCD screen is slightly larger than Fujifilm X100S's 2.8 screen.
Moreover, Nikon D5100 sports a
Fully Articulated screen which you can change the angle and position of the screen almost freely, making it possible to shoot from waist or over-the-head levels, and especially very useful for shooting selfies and video. On the other hand, Fujifilm X100S has a fixed type screen which provides almost no flexibility in shooting positions compared to D5100.