Question
How can we change a camera from $F / 4$ to $F / 5.6 ?$
✓
Answer
The $F$ number of the camera,
$F=\frac{f}{D}$
For F/4 camera, F number is $4,$
$4=\frac{f}{D_{1}}$
For $F/5.6$ camera, $F$ number is $5.6,$
$5.6=\frac{f}{D_{2}}$
$\frac{D_{2}}{D_{1}}=\frac{4}{5.6}$
$\frac{D_{2}}{D_{1}}=\frac{1}{1.412}$
$D_{2}=\frac{D_{1}}{\sqrt{2}}$
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