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-Z400 and Canon SD780 IS side-by-side from the front, back and top in their relative dimensions. Casio EX-Z400 has external dimensions of 95 x 60 x 23 mm (3.74 x 2.36 x 0.91″) and weighs 130 g (0.29 lb / 4.59 oz) (including batteries). Canon SD780 IS has external dimensions of 87 x 56 x 18 mm (3.43 x 2.2 x 0.71″) and weighs 155 g (0.34 lb / 5.47 oz) (including batteries).
Below you can see the front-view size comparison of the Casio EX-Z400 and the Canon SD780 IS. Canon SD780 IS is clearly the smaller of the two cameras. Its body is 8mm narrower, 4mm shorter and 5mm thinner than Casio EX-Z400.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Casio EX-Z400 is significantly lighter (25g ) than the Canon SD780 IS which may become a big advantage especially on long walking trips.
Weather Sealing
Unfortunately neither the Casio Exilim EX-Z400 nor Canon PowerShot SD780 IS (Digital IXUS 100 IS) 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
LCD Screen Size and Features
Casio EX-Z400's 3.00" LCD screen is slightly larger than Canon SD780 IS's 2.5 screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.