Know Your Lens Standard or Normal

In the world of photography, the normal lens or standard lens is a lens that has a range of view is similar to the human eye under normal conditions, hence the normal lens. Why is the standard? first because the point of view that is similar to the human eye so it is not distorted. Second, because the lens with a focal length
Shorter distortion effect whilst widening the lens has a focal length that is longer than a standard lens distortion effect compressed.

Lens with a focal length shorter than the standard lens called a wide angle lens (wide angle). While the lens with a focal length longer than a standard lens called a telephoto lens.

Focal Length Lens Film Camera Era Standard
Standard lens focal length is determined by the size of the camera sensor. A lens with a focal length equal to the diagonal size of the sensor (film) cameras usually called a standard lens. In the era of 35mm film cameras, lenses are all standard lenses with a focal length of 50mm. 50mm size is only approach, because in practice all lenses with a focal length ranges between 40-58 mm lens can be considered standard. Just because a pioneering Leica 35mm format film chooses to make a lens with a focal length of 50 mm that all camera manufacturers follow suit.
Standard Focal Length Lens Digital Camera
In a digital camera, a sensor replaces the film. And the size of a digital camera sensor, in practice there are several kinds. we can know the standard lens focal length for each sensor format as follows:
For the Four Third cameras and Micro Four Third – ie all DSLR and mirrorless cameras Olympus and Panasonic output, standard lens is a lens with a focal length of about 20-25 mm. Example of a standard lens for the format of this sensor is Olympus Zuiko 25mm f/2.8 lens or lens Pancake Panasonic Leica 25mm f/1.4 Summilux.
To format camera with APSC sensor (crop factor of 1.5 x) – almost all DSLR and mirrorless cameras beginner and intermediate classes in addition to full frame, eg Nikon DX – Nikon D3200, Nikon D7000 or Canon 7D, Canon 650D, Sony Alpha 77 or mirrorless Sony NEX-5N. If you have a camera with this sensor format, the standard lens for you is a lens with a focal length of about 25-30 mm. Examples are the lenses: Canon 28mm f/2.8 or Sigma 30mm f/1.4.
For full frame camera that has a sensor size equal to the size of the film – such as the Canon 5D Mark II or Nikon D700, Nikon D800 or Leica M, the standard lens is a lens that has all approaching 50mm focal length. For example, Nikon lens AF-S 50mm f/1.8 or Canon 50mm f/1.2L