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 FZ80 and Sony A58 side-by-side from the front, back and top in their relative dimensions. Panasonic FZ80 has external dimensions of 130 x 94 x 119 mm (5.12 x 3.7 x 4.69″) and weighs 616 g (1.36 lb / 21.73 oz) (including batteries). Sony A58 has external dimensions of 129 x 95 x 78 mm (5.08 x 3.74 x 3.07″) and weighs 492 g (1.08 lb / 17.35 oz) (including batteries).
Below you can see the front-view size comparison of the Panasonic FZ80 and the Sony A58. Sony A58 is 1mm narrower and 41mm thinner than Panasonic FZ80 but it is also 1mm taller. As you can tell, actually this is not a fair size comparison since Panasonic FZ80 has a built-in lens but Sony A58 doesn't. Once you put a lens on A58, its thickness will increase significantly.
Comparison image of the Panasonic FZ80 and the Sony A58 Size, Weight and External Dimensions - Front View
Here is the back view size comparison of the Panasonic FZ80 and Sony A58.
Comparison image of the Panasonic FZ80 and the Sony A58 Size and Weight - Back View
Now lets look at the top view comparison of Panasonic FZ80 and Sony A58.
Top View Comparison image of the Panasonic FZ80 and the the Sony A58 Size
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Sony A58 is significantly lighter (124g ) than the Panasonic FZ80 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 A58, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Panasonic Lumix DMC-FZ80 (Lumix DMC-FZ82) nor Sony SLT-A58 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 Bridge Cameras with Weather Sealing Top DSLR Cameras with Weather Sealing
LCD Screen Size and Features
Panasonic FZ80's 3.00" LCD screen is slightly larger than Sony A58's 2.7" screen.