Lenses
Lenses are named by their focal length. The smaller the focal length, the larger the field of view, and the larger the focal length, the smaller the field of view.
Camera Sensor Size
The size of the camera sensor depends on the manufacturer and camera model.
A full-frame camera sensor has the same size of 36 by 24 millimeters)
Small camera sensors is often called “crop-sensor cameras” because they are crops of bigger sensors.
Using a different sensor size is basically like cropping, the camera sensor size will change the photo’s field of view.
common sensor size:
Full frame( Nikon call it FX)
APS-C ( Nikon call it DX)
Micro 4/3
Crop factor
The size of a full-frame camera sensor, relative to the size of your camera sensor (measured diagonally).
Ultra-wide lenses
Have a focal length of less than 24mm (all of these numbers are in full-frame terms).
Wide-angle lenses
have an equivalent focal length in the range of 24mm to 35mm.
Standard lenses / normal lenses
have focal lengths between 35mm and 70mm.
Telephoto lenses
have focal lengths between 70mm and 300mm.
Super-telephoto lenses
have focal lengths exceeding 300 mm.
Angle of View
angle of view and field of view are often used interchangeably, and it’s how most manufacturers refer to field of view, but they’re not quite the same thing.
The angle of view is the angular size of the view cone. (See diagram above.)
The overall field of view is the maximum area your sensor can capture at a given lens focal length of a lens.
computational formula:
Angle of view (in degrees) = 2 ArcTan (sensor width / ( 2 x focal length))) * (180/π)
Depth of Field
Depth of field is the distance between the closest and farthest objects in a photo that appears acceptably sharp.
Aperture
Aperture is the opening in your lens that lets light pass through to the sensor. Think of it as a pupil for your lens. It dilates to let more light in, and contracts to restrict light when it is bright. Aperture is probably the first thing most photographers think of when they want to adjust the depth of field.
Large apertures, which correlate to small f-stop numbers, produce a very shallow depth of field. On the other hand, small apertures, or large f-stop numbers, produce images with a large depth of field.
factor affecting depth of field
the distance between the camera and the subject. The shorter that distance, the smaller the depth of field.
Wide-angle lenses (short focal lengths) have a deeper depth of field than telephoto lenses (long focal lengths).
cameras with smaller sensors have larger depths of field.