Film photographic exposure

(1) Image magnification: m =1.25cm 400cm =1400.

Vehicle distance: x ≤ 0.1mmm = 0.04m.

Exposure time: t ≤ XV = 0.0410 = 0.04s =1250s.

So the longest exposure time is1250 s.

(2) The aperture size is indicated by a, and the shutter is indicated by b..

Since the exposure of the film remains unchanged, that is, the luminous flux through the lens remains unchanged, there are:

S 1t 1=s2t2

14π(fa 1)2？ 1b 1 = 14π(fa2)2？ 1b2

a2=a 1？ b 1b2= 1 1？ 15250= 1 1×0.2449=2.69

So the combination of shutter and aperture should be 250 and 2.8.

Answer: (1) Maximum exposure time 1250s(2) The combination of shutter and aperture should be 250 and 2.8.