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 Panasonic ZS3 and Pentax S1 side-by-side from the front, back and top in their relative dimensions. Panasonic ZS3 has external dimensions of 103 x 60 x 33 mm (4.06 x 2.36 x 1.3″) and weighs 229 g (0.50 lb / 8.08 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 Panasonic ZS3 and Pentax S1. Pentax S1 is 2mm shorter and 5mm thinner than Panasonic ZS3 but it is also 11mm wider.
Here is the back view size comparison of Panasonic ZS3 and Pentax S1.
Now lets look at the top view comparison of Panasonic ZS3 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 (72g ) than the Panasonic ZS3 which may become a big advantage especially on long walking trips.
Unfortunately neither Panasonic Lumix DMC-ZS3 (Lumix DMC-TZ7) nor Pentax Optio S1 provides any type of weather sealing in their body, 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
Panasonic ZS3's 3" LCD screen is slightly larger than Pentax S1's 2.7" screen.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.