Back focal distance (BFD) (s′F′) is the distance from the vertex of the last optical surface of the system (S2) to the rear focal point (F′). [1][3] Some authors refer to this as "back focal length".

Effective Focal Length – An optical measurement given as the distance from a principal plane of an optical lens to its imaging plane. Back Focal Length – A mechanical measurement given as the …

The back focal length BFL is the distance between the rear vertex V’ of the lens, and the rear focal point F’. Measuring the back focal distance is usually easy. Determining the distance between P’ and V’ is …

Nov 9, 2025 · Back focal length (BFL) is a fundamental measurement in optics that informs the physical design of lens systems. It relates to the distance light travels from the lens to the image sensor or …

The distance from the object to the front lens is called working distance, while the distance from the rear lens to the sensor is called back focal distance. Henceforth, we will be presenting some useful …

Distance from the rear surface of the last element of a lens to the image focal point of the lens. Back focal distance differs from flange focal distance or focal length. Back focal distance value is used …

This video offers an accessible yet insightful journey into the calculation of back focal length, suitable for students, hobbyists, and professionals seeking a deeper und...more