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 Nikon P520 and Panasonic GH4 side-by-side from the front, back and top in their relative dimensions. Nikon P520 has external dimensions of 125 x 84 x 102 mm (4.92 x 3.31 x 4.02″) and weighs 550 g (1.21 lb / 19.40 oz) (including batteries). Panasonic GH4 has external dimensions of 133 x 93 x 84 mm (5.24 x 3.66 x 3.31″) and weighs 560 g (1.23 lb / 19.75 oz) (including batteries).
Below you can see the front-view size comparison of the Nikon P520 and the Panasonic GH4. Nikon P520 is 8mm narrower and 9mm shorter than Panasonic GH4 but it is also 18mm thicker. As you can tell, actually this is not a fair size comparison since Nikon P520 has a built-in lens but Panasonic GH4 doesn't. Once you put a lens on GH4, its thickness will increase significantly.
Here is the back view size comparison of the Nikon P520 and Panasonic GH4.
Now lets look at the top view comparison of Nikon P520 and Panasonic GH4.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Nikon P520 is 10g lighter than the Panasonic GH4 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 GH4, the total kit will weigh much higher.
Weather Sealing
Thanks to the weather-sealed body of the GH4, you can use this camera with more confidence under conditions where there is risk of exposure to water and dust compared to the P520.
LCD Screen Size and Features
Nikon P520's 3.20" LCD screen is slightly larger than Panasonic GH4's 3" screen.