The normal lens on a 35-mm camera has a focal length of 45.0 mm. Its aperture di

Question

The normal lens on a 35-mm camera has a focal length of 45.0 mm. Its aperture diameter varies from a maximum of 16 mm (f/2.8) to a minimum of 2.8 mm(f/16). Determine the resolution limit set by diffraction for f/2.8. Specify as the number of lines per millimeter resolved on the film. Take lambda = 560 nm. Express your answer using two significant figures. Determine the resolution limit set by diffraction for f/16. Specify as the number of lines per millimeter resolved on the film. Take lambda = 560 nm. Express your answer using two significant figures.

Explanation / Answer

In object space, the angular resolution for D as the diameter of the entrance pupil of the imaging lens is
sin = 1.22 {/D};

= 0.56(micrometre) or 0.00056 mm,
D = 35 mm, give
= 1.9 X 10^5 Radian = 3.95 Arc sec.

The diameter of the (first) Airy disc
d = 1.22 N,
sets the limit.

For N = (f/2.8) it is

d = 1.22 [0.00056 mm/2.8] = 0.000244 mm (4098 lines/mm).

b)

For (f/16)

d = 1.22 [0.00056 mm/16] = 0.0000427 mm (23419 lines/mm).

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