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-ZR100 and Nikon D3000 side-by-side from the front, back and top in their relative dimensions. Casio EX-ZR100 has external dimensions of 105 x 59 x 29 mm (4.13 x 2.32 x 1.14″) and weighs 204 g (0.45 lb / 7.20 oz) (including batteries). Nikon D3000 has external dimensions of 126 x 97 x 64 mm (4.96 x 3.82 x 2.52″) and weighs 536 g (1.18 lb / 18.91 oz) (including batteries).
Below you can see the front-view size comparison of the Casio EX-ZR100 and the Nikon D3000. Casio EX-ZR100 is clearly the smaller of the two cameras. Its body is 21mm narrower, 38mm shorter and 35mm thinner than Nikon D3000. As you can tell, actually this is not a fair size comparison since Casio EX-ZR100 has a built-in lens but Nikon D3000 doesn't. Once you put a lens on D3000, its thickness will increase significantly.
Now lets look at the top view comparison of Casio EX-ZR100 and Nikon D3000.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Casio EX-ZR100 is significantly lighter (332g ) than the Nikon D3000 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 D3000, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Casio Exilim EX-ZR100 nor Nikon D3000 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-ZR100 and Nikon D3000's LCD screens have the same diagonal size of 3.00 inches.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.