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 Canon SX400 IS and Panasonic G3 side-by-side from the front, back and top in their relative dimensions. Canon SX400 IS has external dimensions of 104 x 69 x 80 mm (4.09 x 2.72 x 3.15″) and weighs 313 g (0.69 lb / 11.04 oz) (including batteries). Panasonic G3 has external dimensions of 115 x 84 x 47 mm (4.53 x 3.31 x 1.85″) and weighs 336 g (0.74 lb / 11.85 oz) (including batteries).
Below you can see the front-view size comparison of the Canon SX400 IS and the Panasonic G3. Canon SX400 IS is 11mm narrower and 15mm shorter than Panasonic G3 but it is also 33mm thicker. As you can tell, actually this is not a fair size comparison since Canon SX400 IS has a built-in lens but Panasonic G3 doesn't. Once you put a lens on G3, its thickness will increase significantly.
Here is the back view size comparison of the Canon SX400 IS and Panasonic G3.
Now lets look at the top view comparison of Canon SX400 IS and Panasonic G3.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Canon SX400 IS is 23g lighter than the Panasonic G3 but we don't think this will make a significant difference.
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 G3, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Canon PowerShot SX400 IS nor Panasonic Lumix DMC-G3 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 Mirrorless Cameras with Weather Sealing
LCD Screen Size and Features
Canon SX400 IS and Panasonic G3's LCD screens have the same diagonal size of 3.00 inches.
On the other hand, Panasonic G3 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. Canon SX400 IS's LCD screen is a fixed type which provides almost no flexibility in shooting positions compared to G3.