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 Canon SX20 IS and Pentax K-5 side-by-side from the front, back and top in their relative dimensions. Canon SX20 IS has external dimensions of 128 x 88 x 87 mm (5.04 x 3.46 x 3.43″) and weighs 600 g (1.32 lb / 21.16 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 Canon SX20 IS and Pentax K-5. Canon SX20 IS is 3mm narrower and 9mm shorter than Pentax K-5 but it is also 14mm thicker. As you can tell, actually this is not a fair size comparison since Canon SX20 IS has a built-in lens but Pentax K-5 doesn't. Once you put a lens on K-5, its thickness will increase significantly.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Canon SX20 IS is significantly lighter (140g ) 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.
Thanks to the weather sealed body of K-5, you can use this camera with more confidence under conditions where there is risk of exposure to water and dust compared to SX20 IS.
LCD Screen Size and Features
Pentax K-5's 3 LCD screen is slightly larger than Canon SX20 IS's 2.5" screen.
On the other hand, Canon SX20 IS sports a Fully Articulated screen
which you can change the angle and position of the screen almost freely, making it possible to shoot from waist or over the head levels, and especially very useful for shooting selfies and video. On the other hand, Pentax K-5 has a fixed type screen which provides almost no flexibility in shooting positions compared to SX20 IS.