Equivalent Focal Length

03 April 2008 10:02

The term Equivalent Focal Length is used when comparing the effective focal range of lenses designed for use on DSLR cameras with an APS sized sensor to lenses designed to work on cameras with a full frame sensor.

The cropping factor that occurs with the APS sized sensor changes the focal length that the optics of a lens is able to resolve. Accordingly camera manufactures are now producing lenses specifically designed to be used with APS sized sensors. Such lenses have lower values

The viewable image area on DLSR cameras using an APS size sensor is subject to a cropping factor of either 1.5 or 1.6 when compared to that of a full frame sensor.

The cropping factor that occurs when using lenses designed to be used on full frame cameras mean that in associated with lenses designed specifically for use with DSLR cameras. (see DLSR cameras)

To keep the costs and size of DSLR cameras down manufacturers are producing models using a smaller APS sized image sensor (see APS Sensor) to record the image. One of the down sides to using a smaller sensor is the cameras field of view (see field of view) is smaller than it is on cameras using a full frame sensor (see full frame sensor).