Editing Kruithof curve (section)

==Criticism==
While the curve has been used as a guide to design artificial lighting for indoor spaces, with the general suggestion to use sources with low correlated color temperatures (CCT) at low illuminances,<ref>{{cite book|last=Boyce|first=Peter R.|title=Human factors in lighting|year=2003|publisher=Taylor & Francis|location=London|isbn=978-0-7484-0950-1|pages=245–250|edition=2|chapter=Lighting for offices}}</ref> Kruithof did not describe the method of evaluation, the independent variables, nor the test sample that were used to develop the curve. Without these data, nor other validation, the conclusions should not be considered credible. The relationship between illuminance and CCT was not supported by subsequent work.<ref name="Boyce & Cuttle 1990">{{cite journal |last1=Boyce |first1=P.R. |last2=Cuttle |first2=C. |date=1990 |title=Effect of correlated colour temperature on the perception of interiors and colour discrimination |journal=[[Lighting Research & Technology]] |volume=22 |issue=1 |pages=19–36 |doi=10.1177/096032719002200102 |doi-access=free}}</ref><ref name="Davis & Ginthner 1990">{{cite journal|last1=Davis|first1=RG|last2=Ginthner|first2=DN|title=Correlated color temperature, illuminance level and the Kruithof curve|journal=Journal of the Illuminating Engineering Society|date=1990|volume=Winter|pages=27–38|doi=10.1080/00994480.1990.10747937}}</ref>

Illuminance and CCT has been examined in many studies of interior lighting <ref name="Davis & Ginthner 1990" /><ref name="Boyce & Cuttle 1990" /><ref>{{cite journal|last1=Vienot|first1=F|last2=Durand|first2=M|last3=Mahler|first3=E|title=Kruithof's rule revisited using LED illumination|journal=Journal of Modern Optics|date=2009|volume=56|issue=13|pages=1433–1466|doi=10.1080/09500340903151278|bibcode=2009JMOp...56.1433V|s2cid=121921684}}</ref><ref name="Islam et al 2015">{{cite journal|last1=Islam|first1=MS|last2=Dangol|first2=R|last3=Hyvärinen|first3=M|last4=Bhusal|first4=P|last5=Ouolakka|first5=M|last6=Halonen|first6=L|title=User acceptance studies for LED office lighting: Lamp spectrum, spatial brightness and illuminance|journal=Lighting Research and Technology|date=2015|volume=47|pages=54–79|doi=10.1177/1477153513514425|s2cid=109592929 }}</ref><ref name="Wei et al 2014">{{cite journal|last1=Wei|first1=Minchen|last2=Houser|first2=Kevin W.|last3=Orland|first3=Brian|last4=Lang|first4=Dean H.|last5=Ram|first5=Nilam|last6=Sliwinskiwinski|first6=Martin J.|last7=Bose|first7=Mallika|title=Field study of office worker responses to fluorescent lighting of different CCT and lumen output|journal=Journal of Environmental Psychology|volume=39|pages=62–76|doi=10.1016/j.jenvp.2014.04.009|year=2014}}</ref> and these studies consistently demonstrate a different relationship to that suggested by Kruithof.<ref name="Fotios 2017">{{cite journal|last1=Fotios|first1=Steve|title=A Revised Kruithof Graph Based on Empirical Data|journal=LEUKOS|date=2 January 2017|volume=13|issue=1|pages=3–17|doi=10.1080/15502724.2016.1159137|issn=1550-2724|doi-access=free}}</ref> Rather than having upper and lower boundaries, these studies do not suggest CCT to have significant effect and for illuminance suggest only to avoid levels below 300 lux. Current studies have not explored the main critical part that is the low illumination regime or the low CCT range beneath 3000K in general, though some of the studies above reached down to 2850K.  This lacunae in the data is particularly important as it relates to almost all "lifestyle" environments in which lighting designers operate - hotels, restaurants and residential settings.  Further evaluation of these areas would serve well, given the implications for recent learning on [[Light effects on circadian rhythm | the health implications of light on the circadian rhythm]].