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 D90 and Ricoh PX side-by-side from the front, back and top in their relative dimensions. 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). Ricoh PX has external dimensions of 100 x 55 x 21 mm (3.94 x 2.17 x 0.83″) and weighs 156 g (0.34 lb / 5.50 oz) (including batteries).
Below you can see the front-view size comparison of the Nikon D90 and the Ricoh PX. Ricoh PX is clearly the smaller of the two cameras. Its body is 32mm narrower, 48mm shorter and 56mm thinner than Nikon D90. As you can tell, actually this is not a fair size comparison since Ricoh PX 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 Nikon D90 and Ricoh PX.
Now lets look at the top view comparison of Nikon D90 and Ricoh PX.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Ricoh PX is significantly lighter (547g ) 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
Thanks to the weather-sealed body of the PX, you can use this camera with more confidence under conditions where there is risk of exposure to water and dust compared to the D90.
LCD Screen Size and Features
Nikon D90's 3.00" LCD screen is slightly larger than Ricoh PX's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.