Practice question · Sort into groups
Sort each focal length by the class it belongs to on the 24 by 36 mm frame.
Groups: Wide-angle · Normal · Long
- 20 mm
- 28 mm
- 200 mm
- 45 mm
- 85 mm
- 50 mm
Hints
- The normal class sits close to the frame diagonal, so work that diagonal out first.
- Two of the six are within a few millimetres of that diagonal.
Show the answer
Wide-angle: 20 mm, 28 mm
Normal: 50 mm, 45 mm
Long: 85 mm, 200 mm
Why
The classes are defined against the frame diagonal, which is why the same 50 mm lens is normal on 35 mm film, distinctly wide on 6 × 6 and extremely wide on 4 × 5 inch. A focal length has no character of its own until a format is named beside it.
Practise Lenses, Field of View and Depth of Field
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