ak field has a "hot spot" in the centre of the beam. A flat field is essential when using gobos. 
[Arts] 
n., Used in videotape. Videotape runs 30 frames per second. Each frame has two fields, one which scans odd lines and one which
scans even lines. [Arts] 
n., An area of a database record, or graphical user interface form, into which a particular item of data is entered. [Computer and
Information Sciences] 
n., In machine-readable records, the position of a data element or a set of data elements, regarded