DOF guide numbers for telephoto lenses

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Recently Flew pm'd me with a back of the envelope figure of depth of field for a particular lens. It occurred to me that I had no idea how he got that. Is there some source on how to go about finding/calculating these figures? Now that I'm shooting more birds and can see the distance on the lens to the subject and the aperture it would be nice to have some cheat cheet...or handy formula...nah, make that a cheat sheet to see what DOF I can expect on the bird. I know I'm not allowing enough right now.

Thanks, Rich
 

Phil K

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You can find some in the Sigma site. For example, the one for your 120-300 is here.
 
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Excellent Phil. Thanks; that was quick. Even stupid questions are answered in this place! Is the Cafe great or what? And the moderators, not only good looking, but smart....well, some of them!

Rich
 
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from a non-super, non-moderator...

if that's allowed:smile:.

Rich, if you want to know more, download this small calculator (550k)from DL&C. You can use the calculator directly or, after reading the help file, construct a spreadsheet or perhaps enter the equations in your pocket calculator. Or, you can construct your own cheat sheet for selected lenses.
 
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if that's allowed:smile:.

Rich, if you want to know more, download this small calculator (550k)from DL&C. You can use the calculator directly or, after reading the help file, construct a spreadsheet or perhaps enter the equations in your pocket calculator. Or, you can construct your own cheat sheet for selected lenses.

Woo hoo! It gets even better. Thanks very much.

Update Great for PC owners. :frown:

Rich
 
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Bill N

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You might want to also check http://www.tangentsoft.net for a small program called f/calc. It has dof, hyper focal distance, field of view, angle of view, magnification and f stops. It is freeware, nice little program. Good luck, Bill
 
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I once saw a t-shirt with a hyperfocal distance chart on it......upside down, so that as you looked down at your t-shirt, you could read it. :biggrin:

I'm *sure* you could find something like that for DOF too!!!! :biggrin:
 
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Flew made his own (I think) in Excel, and if I can dig it up it has graphs and other cool things...so if you are still looking for one shoot me a PM, and I'm sure I can find it somewhere.
 

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