One of the most difficult things to do is get a great facial record of persons entering a building.  Here are a few tips and considerations to make when attempting this kind of record.

1) Capture faces where you can limit the area and direction a person is facing.  Try to capture them as they are passing through a doorway or hallway, as this is a good way of controlling the direction they are moving/facing. 

2) Use a verifocal lens and limit the viewable image when seen through the lens to only the area persons' heads will be traveling.  This camera serves one purpose: faces.  The other cameras in your system will record their clothes, actions, etc.  It is of the utmost importance that you have the largest image possible of their face, as size directly translates to detail and recognizability. 

3) Set your DVR to the highest quality and largest image possible.  Frame rate is not as important for this camera, because people do not typically move fast enough to obscure their face.

4) Use very high quality cameras.  High resolution means clarity.  Additionally cameras with WDR features are especially useful during the day to help combat the blinding effects of the sun.

5) Shoot level if possible.  The closer you can get to a square shot at the face, the better.  Shooting at an angle means you will capture (at least in part) the side of someone's face or the top of their head.  You want a mug shot.

These concepts can be also applied to license plates, cash registers, counter spaces, card tables and just about any other situation where details are important.  In some scenarios (such as license plates and some cash situations) the frame rate becomes more important as speed does also become a factor.    For these scenarios a 30 frames per second @ 4CIF or D1 resolution may be required.