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 400D and Panasonic FZ100 side-by-side from the front, back and top in their relative dimensions. Canon 400D has external dimensions of 127 x 94 x 65 mm (5 x 3.7 x 2.56″) and weighs 556 g (1.23 lb / 19.61 oz) (including batteries). Panasonic FZ100 has external dimensions of 124 x 82 x 92 mm (4.88 x 3.23 x 3.62″) and weighs 540 g (1.19 lb / 19.05 oz) (including batteries).
Below you can see the front view size comparison of Canon 400D and Panasonic FZ100. Panasonic FZ100 is 3mm narrower and 12mm shorter than Canon 400D but it is also 27mm thicker. As you can tell, actually this is not a fair size comparison since Panasonic FZ100 has a built-in lens but Canon 400D doesn't. Once you put a lens on 400D, its thickness will increase significantly.
Now lets look at the top view comparison of Canon 400D and Panasonic FZ100.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Panasonic FZ100 is 16g lighter than the Canon 400D 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 400D, the total kit will weigh much higher.
Unfortunately neither Canon EOS 400D (EOS Digital Rebel XTi / EOS Kiss Digital X) nor Panasonic Lumix DMC-FZ100 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 DSLR Cameras with Weather Sealing Top Bridge Cameras with Weather Sealing
LCD Screen Size and Features
Panasonic FZ100's 3" LCD screen is slightly larger than Canon 400D's 2.5" screen.
Moreover, Panasonic FZ100 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, Canon 400D has a fixed type screen which provides almost no flexibility in shooting positions compared to FZ100.