Definition of back focus in English:

back focus

Syllabification: back fo·cus

noun

Photography
The distance between the back of a lens and the image of an object at infinity.
More example sentences
  • If the focal length is positive and the back focus B is longer than the focal length, the result is a reversed telephoto, or retrofocus.

Definition of back focus in:

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Word of the day apposite
Pronunciation: ˈapəzɪt
adjective
apt in the circumstances or relation to something