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 Samsung TL225 and Pentax K-500 side-by-side from the front, back and top in their relative dimensions. Samsung TL225 has external dimensions of 100 x 60 x 19 mm (3.94 x 2.36 x 0.75″) and weighs 187 g (0.41 lb / 6.60 oz) (including batteries). Pentax K-500 has external dimensions of 130 x 97 x 71 mm (5.12 x 3.82 x 2.8″) and weighs 646 g (1.42 lb / 22.79 oz) (including batteries).
Below you can see the front-view size comparison of the Samsung TL225 and the Pentax K-500. Samsung TL225 is clearly the smaller of the two cameras. Its body is 30mm narrower, 37mm shorter and 52mm thinner than Pentax K-500. As you can tell, actually this is not a fair size comparison since Samsung TL225 has a built-in lens but Pentax K-500 doesn't. Once you put a lens on K-500, its thickness will increase significantly.
Now lets look at the top view comparison of Samsung TL225 and Pentax K-500.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Samsung TL225 is significantly lighter (459g ) than the Pentax K-500 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-500, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Samsung TL225 (ST550) nor Pentax K-500 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 Compact Cameras with Weather Sealing Top DSLR Cameras with Weather Sealing
LCD Screen Size and Features
Samsung TL225's 3.50" LCD screen is slightly larger than Pentax K-500's 3 screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.