
There are several online depth of field calculators around but I do like this one from Don Fleming. It’s bang up to date with all the latest D-SLR models, and makes the proper adjustment for a full frame sensor compared to an APS-C sized sensor. Did you know that shooting at f/5.6 on a D300 gives the equivalent depth of field of f/8 on an older Hasselblad? Read David Ziser’s post at Digital Pro Talk for a great argument on how using lower f stops is possible with digital equipment.
I like the DOF calculator as a quick reference – for example here I can see shooting at a subject 10 feet away using a 50mm lens at f/2.8, objects just under a foot in front of the subject and just over a foot behind will also be in focus. A graphical representation is shown as well, example below.
Try the online depth of field calculator here, hope you find it useful!

I’ve got some bad news if you’ve been saving up for the monster 


Nikon D100, 24-85mm @ 85mm, 1/60th at f/4.5, on camera flash