In heraldry the background of the shield is called the field . The field is usually composed of one or more tinctures (colours or metals) or furs.
In extremely rare cases, the field is not a tincture, but may be a landscape. Arthur Charles Fox-Davies, in his Art of Heraldry, states that while there are many coats in British heraldry in which the charges make up a landscape, there is only one, the arms of Lopes, where the field itself is so described: "In a landscape field, a fountain, therefrom issuing a palm-tree all proper." However, Fox-Davies is incorrect, as in 1751 Robert Dinwiddie in Scotland was granted a coat of the following blazon: Party per Fesse two landskips the first (the uppermost) holding a wild Indian at full draught his bow bent, marking at a stag standing at full Gaze Regardant proper The Emblem of the Earth, And in base, the Emblem of water with a sloop under sail, within sight of and making towards a distant land Representing America.[1] (http://www.heraldry-scotland.co.uk/Homepage.htm) Landscape fields are regarded by many heralds as unheraldic and deprecated, as they cannot be consistently drawn from blazon.
Being near the field and unarmored, this is for your own safety.
The field herald should always have the pairings (such as on pairs of index cards) for at least the next two bouts in their ring (also called a "field" or "eric").
The Lead FH should have a convention for which field herald should announce the next set of arming calls if two field heralds are ready at the same time.