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 D80 and Olympus SP-800 UZ side-by-side from the front, back and top in their relative dimensions. Nikon D80 has external dimensions of 132 x 103 x 77 mm (5.2 x 4.06 x 3.03″) and weighs 668 g (1.47 lb / 23.56 oz) (including batteries). Olympus SP-800 UZ has external dimensions of 110 x 90 x 91 mm (4.33 x 3.54 x 3.58″) and weighs 455 g (1.00 lb / 16.05 oz) (including batteries).
Below you can see the front view size comparison of Nikon D80 and Olympus SP-800 UZ. Olympus SP-800 UZ is 22mm narrower and 13mm shorter than Nikon D80 but it is also 14mm thicker. As you can tell, actually this is not a fair size comparison since Olympus SP-800 UZ has a built-in lens but Nikon D80 doesn't. Once you put a lens on D80, its thickness will increase significantly.
Now lets look at the top view comparison of Nikon D80 and Olympus SP-800 UZ.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Olympus SP-800 UZ is significantly lighter (213g ) than the Nikon D80 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 D80, the total kit will weigh much higher.
Unfortunately neither Nikon D80 nor Olympus SP-800 UZ provides any type of weather sealing in their body, 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
Olympus SP-800 UZ's 3" LCD screen is slightly larger than Nikon D80's 2.5" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.