Original sentence: The F-number in this lens refers only to the depth-of-field produced by its use.The T-number refers to the brightness of light which passes through the lens and is collected on the film or sensor
Edited sentence: The F-number in this lens refers to the effective aperture opening and determines the depth-of-field produced by its use.The T-number refers to the amount of light which passes through the lens and is collected on the film or sensor in relation to a lens without an apodization element