Commercial Defensive Shields are normally manufactured to admit all wavelengths from the very short-wave radio through gamma rays, and emit longer-wave radio. Though it might seem foolish to admit such dangerous wavelengths as the gamma and X ray wavelengths, the common decision has heen that it is far better to expose oneself to a little background radiation than it is to have one's shield emitting dangerous radiation during a fight, possibly endangering unshielded bystanders. The ill effects of the radio emissions, on the other hand, cause, at worst, a bad bout of static in the immediate neighborhood. Special shields have heen manufactured on occasion to take advantage of the radiational HOLTZMAN EFFECT 313 HOLTZMAN EFFECT properties of the planar field: among artists and dye-makers, who are interested in planar fields which admit or reflect only a single, precise color (or group of colors); or for cosmetic uses (by muling all of the colors except yellow, one can conceal a pallor); or for jailors, who normally transport prisoners in Shields which admit no visible spectra; or for those desiring Shields which emit only a single wavelength of gamma rays (this variation has been used by assassins in several particularly vicious exercises of kanly); or, most recently, for the development of Shields which specifically do not emit in the three-kilocycle radio bandwidth, for special use on Arrakis, where the local fauna is sensitive to radio transmissions on that bandwidth and tends to devour any source of such a transmission, even one as diffuse as that from a personal Shield. Matter above certain densities is repelled by the inside surface of a planar field, and it is this repellent property which made the Personal Defensive Shield a possibility. When a planar field node is being manufactured, the plane of the effect can be warped with a great deal Of freedom: whenever a planar field is warped so as to intersect with itself, the shield fuses into a seamless connection. (If not warped, men the effect forms a flat plane with an area dependent upon the amount of energy used in its consmiction.) Planar effect fields which are warped tend to contract towards their geometric centers, but cannot contract fully if obstructed by matter in concentrations above the critical density. Since planar effect fields are infinitely elastic (given enough power, of course), and infinitely malleable, so long as topographic identity is maintained, they are usually produced in globular or hemispherical formats: when placed around an object, the field contracts to within a few centimeters of the object being ert globed. A field's shape can be freely and instantly altered from the inner side: when any mass is moved toward the inner side at less man the reflection velocity of the field, the field in that region is instantly repelled by the mass, and the field stretches into a new shape, as required.