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 D40X and Pentax S1 side-by-side from the front, back and top in their relative dimensions. Nikon D40X has external dimensions of 124 x 94 x 64 mm (4.88 x 3.7 x 2.52″) and weighs 522 g (1.15 lb / 18.41 oz) (including batteries). Pentax S1 has external dimensions of 114 x 58 x 28 mm (4.49 x 2.28 x 1.1″) and weighs 157 g (0.35 lb / 5.54 oz) (including batteries).
Below you can see the front-view size comparison of the Nikon D40X and the Pentax S1. Pentax S1 is clearly the smaller of the two cameras. Its body is 10mm narrower, 36mm shorter and 36mm thinner than Nikon D40X. As you can tell, actually this is not a fair size comparison since Pentax S1 has a built-in lens but Nikon D40X doesn't. Once you put a lens on D40X, its thickness will increase significantly.
Here is the back view size comparison of the Nikon D40X and Pentax S1.
Now lets look at the top view comparison of Nikon D40X and Pentax S1.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Pentax S1 is significantly lighter (365g ) than the Nikon D40X 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 D40X, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Nikon D40X nor Pentax Optio S1 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 DSLR Cameras with Weather Sealing Top Compact Cameras with Weather Sealing
LCD Screen Size and Features
Pentax S1's 2.70" LCD screen is slightly larger than Nikon D40X's 2.5 screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.