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 Nikon L31 and Nikon D3 side-by-side from the front, back and top in their relative dimensions. Nikon L31 has external dimensions of 96 x 59 x 29 mm (3.78 x 2.32 x 1.14″) and weighs 160 g (0.35 lb / 5.64 oz) (including batteries). Nikon D3 has external dimensions of 160 x 157 x 88 mm (6.3 x 6.18 x 3.46″) and weighs 1300 g (2.87 lb / 45.86 oz) (including batteries).
Below you can see the front view size comparison of Nikon L31 and Nikon D3. Nikon L31 is clearly the smaller of the two cameras. Its body is 64mm narrower, 98mm shorter and 59mm thinner than Nikon D3. As you can tell, actually this is not a fair size comparison since Nikon L31 has a built-in lens but Nikon D3 doesn't. Once you put a lens on D3, its thickness will increase significantly.
Here is the back view size comparison of Nikon L31 and Nikon D3.
Now lets look at the top view comparison of Nikon L31 and Nikon D3.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Nikon L31 is significantly lighter (1140g ) than the Nikon D3 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 D3, the total kit will weigh much higher.
Thanks to the weather sealed body of D3, you can use this camera with more confidence under conditions where there is risk of exposure to water and dust compared to L31.
LCD Screen Size and Features
Nikon D3's 3" LCD screen is slightly larger than Nikon L31's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.