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 Panasonic GM1 and Canon SX40 HS side-by-side from the front, back and top in their relative dimensions. Panasonic GM1 has external dimensions of 99 x 55 x 30 mm (3.88 x 2.16 x 1.2″) and weighs 204 g (0.45 lb / 7.20 oz) (including batteries). Canon SX40 HS has external dimensions of 123 x 92 x 108 mm (4.84 x 3.62 x 4.25″) and weighs 600 g (1.32 lb / 21.16 oz) (including batteries).
Below you can see the front-view size comparison of the Panasonic GM1 and the Canon SX40 HS. Panasonic GM1 is clearly the smaller of the two cameras. Its body is 24mm narrower, 37mm shorter and 78mm thinner than Canon SX40 HS. As you can tell, actually this is not a fair size comparison since Canon SX40 HS has a built-in lens but Panasonic GM1 doesn't. Once you put a lens on GM1, its thickness will increase significantly.
Here is the back view size comparison of the Panasonic GM1 and Canon SX40 HS.
Now lets look at the top view comparison of Panasonic GM1 and Canon SX40 HS.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Panasonic GM1 is significantly lighter (396g ) than the Canon SX40 HS 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 GM1, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Panasonic Lumix DMC-GM1 nor Canon PowerShot SX40 HS 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 Mirrorless Cameras with Weather Sealing Top Bridge Cameras with Weather Sealing
LCD Screen Size and Features
Panasonic GM1's 3.00" LCD screen is slightly larger than Canon SX40 HS's 2.7 screen.