Wavelength-range definition for purple radiation according to ISO or
imagers in the Landsat satellites.
Usage
Purple(std = "ISO")
Value
A waveband object defining a wavelength range.
Arguments
std
a character string "ISO", or Landsat imager "LandsatOLI".
Details
Purple (or violet) wavelengths as defined by ISO standards based on
human vision overlap the UVA band as defined by a separate ISO standard.
In other contexts like plant photobiology purple is included under blue,
while some overoptimistic LED sellers call LEDs emitting in the violet
region ultraviolet LEDs. In addition to the ISO definition of purple,
a purple channel from Landsat imagers is implemented.