Constructor of far-red wavebandSource:
Wavelength-range definitions for far-red light according as commonly used in plant or remote sensing applications.
a character string, defaults to "ISO", as for other colour definitions, which in this case returns
The different arguments passed to formal parameter
determine the range of wavelengths set as boundaries of the returned
waveband object; far-red in not defined by
definitions based on human colour vision, and included under red;
"Broad" are non-standard but used in plant
"RedEdge40" are non-standard but
frequently used in remote sensing.
In plant photobiology the definitions proposed by Prof. Harry Smith are the most widely used, specially to compute a red to far-red photon ratio relevant to phytochrome photoreceptors. However, other authors have used different definitions in their publications. "Smith10" (725-735 nm), "Smith20" (720-740 nm), "Inada" (700-800 nm), "Warrington" (700-850 nm), and "Sellaro" (700-750 nm).
Other definitions used in remote sensing. For example the "red edge" is to detect the condition of vegetation based on light reflectance by green vegetation. These bands are centred at the reflectance transition in the far-red band (725 nm), and here we define "RedEdge40" (705-745 nm) and "RedEdge20" (715-735 nm).
The bands are defined as square windows, these can be applied to spectral data to obtain the "true" values, but they do not simulate the sensitivity of broad-band sensors or the spectral transmittance of ionic filters. Some band-pass interference filters may have very sharp cut-in and cut-off, and their effect can be approximated by a square window, but filters based on light absorption will show gradual tails and bell-shaped wavelength-windows.
Aphalo, P. J., Albert, A., Björn, L. O., McLeod, A. R., Robson, T. M., Rosenqvist, E. (Eds.). (2012). Beyond the Visible: A handbook of best practice in plant UV photobiology (1st ed., p. xxx + 174). Helsinki: University of Helsinki, Department of Biosciences, Division of Plant Biology. ISBN 978-952-10-8363-1 (PDF), 978-952-10-8362-4 (paperback). Open access PDF download available at doi:10.31885/9789521083631 .
ISO (2007) Space environment (natural and artificial) - Process for determining solar irradiances. ISO Standard 21348. ISO, Geneva.
Murakami, K., Aiga I. (1994) Red/Far-red photon flux ratio used as an index number for morphological control of plant growth under artificial lighting conditions. Proc. Int. Symp. Artificial Lighting, Acta Horticulturae, 418, ISHS 1997.
Sellaro, R., Crepy, M., Trupkin, S. A., Karayekov, E., Buchovsky, A. S., Rossi, C., & Casal, J. J. (2010). Cryptochrome as a sensor of the blue/green ratio of natural radiation in Arabidopsis. Plant physiology, 154(1), 401-409. doi:10.1104/pp.110.160820 .
Smith, H. (1982) Light quality, photoperception and plant strategy. Annual Review of Plant Physiology, 33:481-518. doi:10.1146/annurev.pp.33.060182.002405
Far_red() # no ISO definition exists #> 'ISO gives no standard definition of far-red. #> Not available #> low (nm) NA #> high (nm) NA #> weighted none Far_red("ISO") # no ISO definition exists #> 'ISO gives no standard definition of far-red. #> Not available #> low (nm) NA #> high (nm) NA #> weighted none Far_red("Smith10") # 10 nm wide #> FarRed.Smith10 #> low (nm) 725 #> high (nm) 735 #> weighted none Far_red("Smith20") # 20 nm wide #> FarRed.Smith20 #> low (nm) 720 #> high (nm) 740 #> weighted none Far_red("Inada") #> FarRed.Inada #> low (nm) 700 #> high (nm) 800 #> weighted none Far_red("Warrington") #> FarRed.Warrington #> low (nm) 700 #> high (nm) 850 #> weighted none Far_red("Sellaro") #> FarRed.Sellaro #> low (nm) 700 #> high (nm) 750 #> weighted none Far_red("RedEdge40") #> FarRed.RedEdge40 #> low (nm) 705 #> high (nm) 745 #> weighted none Far_red("RedEdge20") #> FarRed.RedEdge20 #> low (nm) 715 #> high (nm) 735 #> weighted none e_irrad(sun.spct, Far_red("Smith10")) # W m-2 #> E_FarRed.Smith10 #> 4.065679 #> attr(,"time.unit") #>  "second" #> attr(,"radiation.unit") #>  "total energy irradiance" q_irrad(sun.spct, Far_red("Smith10")) # mol m-2 #> Q_FarRed.Smith10 #> 2.481642e-05 #> attr(,"time.unit") #>  "second" #> attr(,"radiation.unit") #>  "total photon irradiance" q_irrad(sun.spct, Far_red("Smith10"), scale.factor = 1e6) # umol m-2 #> Q_FarRed.Smith10 #> 24.81642 #> attr(,"time.unit") #>  "second" #> attr(,"radiation.unit") #>  "total photon irradiance"