Watch the video: What is focal length? Take two 50mm lenses: an f/1.8 and an f/1.2. Even though they both have the same 50mm focal length, they're not the same physical length – and neither of them is ...

A 2″ eyepiece delivers a wider true field of view (the actual amount of sky visible) than a 1¼” eyepiece of the same focal length. Two factors determine the true field: the telescope’s focal length ...

Focal length is the optical distance in millimeters between a camera lens and the sensor or film. It determines the height and width of the scene being captured, known as the "field of view." A prime ...