I was really looking for some type of quick rule of thumb formula






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<td width="4%" valign="top"]<span style="font-size: x-small; font-family: Arial;"]1.</td>
<td width="96%"]<span style="font-size: x-small; font-family: Arial;"]Larger F-numbers give greater depth of field. . </td>
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<td width="4%" valign="top"]<span style="font-size: x-small; font-family: Arial;"]2.</td>
<td width="96%"]<span style="font-size: x-small; font-family: Arial;"]Shorter focal lengths give greater depth of field. </td>
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<td width="4%" valign="top"]<span style="font-size: x-small; font-family: Arial;"]3.</td>
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<span style="font-size: x-small; font-family: Arial;"]Greater subject distance gives greater depth of field.


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<td width="4%" valign="top"]<span style="font-size: x-small; font-family: Arial;"]4.</td>
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<span style="font-size: x-small; font-family: Arial;"]Depth of field is greater behind the subject than in front


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<span style="font-size: x-small; font-family: Arial;"]eg. 50mm f/4 25 feet depth of field = 12 ft (standard)


<span style="font-size: x-small; font-family: Arial;"] 50mm f/8 25 feet depth of field =29 feet(2x f stop)


<span style="font-size: x-small; font-family: Arial;"] 25mm f/4 25 feet depth of field = 314 feet (1/2 focal lenght)


<span style="font-size: x-small; font-family: Arial;"]<span style="font-size: x-small; font-family: Arial;"] 50 mm f/4 50 feet depth of field =58 feet (2x distance)


<span style="font-size: x-small; font-family: Arial;"]If we look at the factors thatchangefocal lenght it appears that the F stop has the greatest affect


<span style="font-size: x-small; font-family: Arial;"]I was looking for something like:


<span style="font-size: x-small; font-family: Arial;"]double the F stop squares the distance (approx) 12 squared = 144


<span style="font-size: x-small; font-family: Arial;"]do we have a calculus expert out there?


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