In Photography world , oftenly you will hear photographers talk about Focal Lenght, but do you know what focal lenght is? In some cases many beginner photographer ashame to ask about it, even they oftenly use many different lenses but basicly they don’t know the concepts of focal lenght. So here i will explain about focal length.
Literally, Focal Lenght is hte lenght between lens and focal area (censor in digital camera or film in old camera) where your photo was made, to make it simple take a look the illustration bellow:
Focal lenght is measured in milimeter (mm) and symbolyzed by f.
Now the question is what the focal lenght for? Focal Lenght determine how wide the field of view/ pointview of lens. More short the focal lenght, more wide the view in the camera frame. More long focal lenght , more small the view in the camera frame. Lns with the short focal lenght usually called Wide Angle Lens.Lens with the long focal lenght usually called as Tele lens ( read also the types of digital camera lens).
To make more understand the relation between focal lenght and field of view, look at example bellow:
The sample pictures above explain the different of field of view on same photoshoot lenght. When using focal lenght 18 mm (wide angle), you can shoot the foreground building, the lake , and the bulding acroos the lake. When using focal lenght 50 mm (normal) you can shoot the lake and building across the lake. When using focal lenght 100 mm (Medium Telephoto) you can shoot the just the buiding across the lake. When you using focal lenght 200 mm you can soot the tower . When you usiing Focal Lenght 300 mm you can shoot the top part of tower.
So, if the focal lenght of lens is 200 mm, then the real lenght is 200 mm (20 cm). It doesn’t have to. Modern lens with the advanced optic technology using many aditional elements inside that work in combination, so the the real lenght of lense can be shorter.
source images : otodidak, digital camera world
