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-Z450 and Pentax K-5 side-by-side from the front, back and top in their relative dimensions. Casio EX-Z450 has external dimensions of 81 x 56 x 21 mm (3.19 x 2.2 x 0.83″) and weighs 128 g (0.28 lb / 4.52 oz) (including batteries). Pentax K-5 has external dimensions of 131 x 97 x 73 mm (5.16 x 3.82 x 2.87″) and weighs 740 g (1.63 lb / 26.10 oz) (including batteries).
Below you can see the front-view size comparison of the Casio EX-Z450 and the Pentax K-5. Casio EX-Z450 is clearly the smaller of the two cameras. Its body is 50mm narrower, 41mm shorter and 52mm thinner than Pentax K-5. As you can tell, actually this is not a fair size comparison since Casio EX-Z450 has a built-in lens but Pentax K-5 doesn't. Once you put a lens on K-5, its thickness will increase significantly.
Here is the back view size comparison of the Casio EX-Z450 and Pentax K-5.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Casio EX-Z450 is significantly lighter (612g ) than the Pentax K-5 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 K-5, the total kit will weigh much higher.
Weather Sealing
Thanks to the weather-sealed body of the K-5, you can use this camera with more confidence under conditions where there is risk of exposure to water and dust compared to the EX-Z450.
LCD Screen Size and Features
Casio EX-Z450 and Pentax K-5'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.