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 P300 and Nikon 1 J3 side-by-side from the front, back and top in their relative dimensions. Nikon P300 has external dimensions of 103 x 58 x 32 mm (4.06 x 2.28 x 1.26″) and weighs 189 g (0.42 lb / 6.67 oz) (including batteries). Nikon 1 J3 has external dimensions of 101 x 61 x 29 mm (3.98 x 2.4 x 1.14″) and weighs 201 g (0.44 lb / 7.09 oz) (including batteries).
Below you can see the front-view size comparison of the Nikon P300 and the Nikon 1 J3. Nikon 1 J3 is 2mm narrower and 3mm thinner than Nikon P300 but it is also 3mm taller. As you can tell, actually this is not a fair size comparison since Nikon P300 has a built-in lens but Nikon 1 J3 doesn't. Once you put a lens on 1 J3, its thickness will increase significantly.
Now lets look at the top view comparison of Nikon P300 and Nikon 1 J3.
Weight is another important factor, especially when deciding on a camera that you want to carry with you all day.
Nikon P300 is 12g lighter than the Nikon 1 J3 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 1 J3, the total kit will weigh much higher.
Weather Sealing
Unfortunately neither the Nikon Coolpix P300 nor Nikon 1 J3 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
Nikon P300 and Nikon 1 J3's LCD screens have the same diagonal size of 3.00 inches.
Unfortunately, both cameras has fixed screens so they don't tilt or flip in directions.