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 Panasonic ZS15 and Nikon P7800 side-by-side from the front, back and top in their relative dimensions. Panasonic ZS15 has external dimensions of 105 x 58 x 33 mm (4.13 x 2.28 x 1.3″) and weighs 208 g (0.46 lb / 7.34 oz) (including batteries). Nikon P7800 has external dimensions of 119 x 78 x 50 mm (4.69 x 3.07 x 1.97″) and weighs 399 g (0.88 lb / 14.07 oz) (including batteries).
Below you can see the front view size comparison of Panasonic ZS15 and Nikon P7800. Panasonic ZS15 is clearly the smaller of the two cameras. Its body is 14mm narrower, 20mm shorter and 17mm thinner than Nikon P7800.
Here is the back view size comparison of Panasonic ZS15 and Nikon P7800.
Now lets look at the top view comparison of Panasonic ZS15 and Nikon P7800.
Weight is another important factor especially when deciding on a camera that you want to carry with you all day.
Panasonic ZS15 is significantly lighter (191g ) than the Nikon P7800 which may become a big advantage especially on long walking trips.
Unfortunately neither Panasonic Lumix DMC-ZS15 (Lumix DMC-TZ25) nor Nikon Coolpix P7800 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 Compact Cameras with Weather Sealing
LCD Screen Size and Features
Panasonic ZS15 and Nikon P7800's LCD screens has the same diagonal size of 3".
On the other hand, Nikon P7800 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. Panasonic ZS15's LCD screen is a fixed type which provides almost no flexibility in shooting positions compared to P7800.