Don't speculate go here
DOF DOF2
pay attention to here:
Understanding Depth of Field in Photography great place for tutorials.
Go here for DoF calculators - one that you can customize for your own use and create DoF Scales for focal lengths you have.
Hyperfocal Distance and Depth of Field Calculator - DOFMaster
Go here to see the calculations for DoF. The calculations are effected by the CoC (Circle of Confusion) which has to do with reproduction size, lens resolution capabilities and sensor resolution.
Depth of field - Wikipedia, the free encyclopedia
The issue with selective focus via DoF and the ability to control what is out of focus and what part of the subject is in focus, has more to do with the camera than anything else. P&S cameras have very small lenses (f stop wise) and very small sensors. The DoF on these cameras is not controllable as in a DSLR - that control is one reason to buy a DSLR so you can have that control.
On a sensor that is smaller than a 135 format (so called full frame) the depth of field for a given focal length is slightly different. At 50mm on my K10D at f/8.0 the DoF when focused at infinity - anything beyond 12.6 meters is in focus. On 35mm film it is 10.5 meters to infinity, on a 4x5 it is 4.47 meters. The general rule is that the bigger the sensor the greater the depth of field for a given focal length and f/stop. However, on smaller sensors a 50mm lens has a smaller FoV and therefore is more of a telephoto. On my old (now dead) P&S its max focal length was 5mm with a 2.2 MP sensor. I had no control over DoF and for that device the DoF was huge. On the first camera I used (a Brownie Box using 620 roll film with an image of 2.5 x 3.5 inches) it had one shutter speed (1/30) and two f stops - wide open at f/8 and closed down at f/11. No focus per say as the lens was focused at infinity, the closest focus was about 5 feet.
Experiment and calculate so you can learn how to exploit DoF, speculation will lead to frustration. Don't base your actions on others "opinions" - including mine - do the research and figure it out.
The Elitist - formerly known as PDL