Focal length, in millimetres, describes how wide or tight a lens looks on a given sensor. 24mm on full frame is wide; 85mm is tighter and more compressed. The same number looks tighter on Super 35 or APS-C than on full frame. Cinematographers pick millimetres for emotion, not only to “fit the subject.”
When you rent, name the camera body so the vendor can confirm mount and vignetting. Pair lens rental with a DP or camera operator who already knows the set.