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 Casio EX-100 and Nikon D90 side-by-side from the front, back and top in their relative dimensions. Casio EX-100 has external dimensions of 119x67x50 mm and weighs 389 g (including batteries). Nikon D90 has external dimensions of 132 x 103 x 77 mm (5.2 x 4.06 x 3.03″) and weighs 703 g (1.55 lb / 24.80 oz) (including batteries).
Below you can see the front-view size comparison of the Casio EX-100 and the Nikon D90. Casio EX-100 is clearly the smaller of the two cameras. Its body is 13mm narrower, 36mm shorter and 27mm thinner than Nikon D90. As you can tell, actually this is not a fair size comparison since Casio EX-100 has a built-in lens but Nikon D90 doesn't. Once you put a lens on D90, its thickness will increase significantly.
Here is the back view size comparison of the Casio EX-100 and Nikon D90.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Casio EX-100 is significantly lighter (314g ) than the Nikon D90 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 D90, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Casio Exilim EX-100 nor Nikon D90 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 Compact Cameras with Weather Sealing Top DSLR Cameras with Weather Sealing
LCD Screen Size and Features
Casio EX-100's 3.50" LCD screen is slightly larger than Nikon D90's 3" screen.
In addition to the size advantage, Casio EX-100 LCD screen also has a
Tilting feature where you can change the angle of the screen to make it easier to shoot from waist or over-the-head levels. On the other hand, Nikon D90 has a fixed type screen which provides less flexibility in shooting positions compared to EX-100.