Practice question · Multiple choice
A lens is described as 'normal' relative to the format diagonal, not because of an absolute optical constant. If a 50 mm optic is transferred from a 24 × 36 mm film body to a much smaller sensor, what follows for its role?
Hints
- How is a 'normal' lens defined in relation to sensor dimensions?
- What happens to the angle of view when the focal length remains constant but the active image area shrinks?
Show the answer
C. It functions as a telephoto optic due to a narrower angle of view
Why
A focal length is only 'normal' when close to the format diagonal (~43 mm for 35 mm film). On smaller sensors, that same focal length covers a narrower angle of view, acting as a telephoto lens rather than a normal or wide lens.
Practise Lenses, Field of View and Depth of Field
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