Depth of Field

[iND]

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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<span style="font-size: x-small; font-family: Arial;"]Greater subject distance gives greater depth of field.


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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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[iND]

Sorry I should have stated that the focal lenght of the lens appears to have the largest affect on the depth of field, followed by the F stop


Surely there is a quick rule of thumb here.

[Stephen Probert]

Wikipedia has some formulas, but they do not condense well to rules of thumb. That is probably why people carry tables with depth of field on them. I printed out 4 tables on 2 notecards with common focal lengths. My idea is to reference these, or study them while shooting in non-pressure situations until I just get more familiar with what focal length/aperture/subject distance give what kind of depth of field. I haven't spent much time on it and it will probably be difficult and take many years. I would think if someone like a wedding photographer who primarily shot with a 35mm and 85mm lens or something like that, might be able to almost memorize the depth of field characteristics for those two lenses, but for zooms.....?


http://en.wikipedia.org/wiki/Depth_of_field

[asmodai]

Your best bet for quickies is to commit a few common conditions to memory. As in: "My 50mm at Xpaces at f/x.x provides Xfeet of in focus area, and Xfeet at x+2 paces", for each of your lenses. Once you know those you can wiggle around each memorized point with a few degrees of freedom.








Maybe one day each camera will have a little range-finder and an in-viewfinder display of present DOF size.