We consider a lower weight better because lighter devices are more comfortable to carry. A lower weight is also an advantage for home appliances, as it makes transportation easier, and for many other types of products.
2.has an optical viewfinder
An optical viewfinder (or OVF) allows the photographer to compose a shot while seeing exactly what the lens will capture. OVFs have no time lag and require no power - as opposed to electronic viewfinders, which can drain battery life. OVFs are also better in low light situations.
A hot shoe can be used to attach an external flash, as well as light meters, viewfinders, rangefinders and other attachments.
A system camera has many interchangeable components such as lenses, flashes, and other accessories. System cameras offer greater flexibility than compact cameras.
You can operate the device easily, by pressing the screen with your fingers.
A flash is good for low-light environments, and can sometimes be used as flashlight.