Editing Kruithof curve (section)

==Further studies==
The Kruithof curve, as presented, does not contain experimental data points and serves as an approximation for desirable lighting conditions. Therefore, its scientific accuracy has been reassessed.

Color rendering index is a [[Units of measurement|metric]] for describing the [[Visual appearance|appearance]] of a source and whether or not it is considered pleasing. The color rendering index of a given source is a measure of that source's ability to faithfully reproduce colors of an object. Light sources, like [[candle]]s or incandescent light bulbs produce spectrums of [[Electromagnetic spectrum|electromagnetic]] energy that closely resemble Planckian black bodies; they look much like natural sources. Many fluorescent lamps or [[LED lamp|LED light bulbs]] have spectrums that do not match those of Planckian blackbodies and are considered unnatural. Therefore, the way that they render the perceived colors of an environment may be also considered unnatural. While these newer sources can still achieve correlated color temperatures and illuminance levels that are within the comfortable region of the Kruithof curve, variability in their color rendering indices may cause these sources to ultimately be displeasing.

Different activities or scenarios call for different color temperature–illuminance pairs: preferred light sources change depending on the scenario the source is illuminating.<ref>{{cite tech report|url=http://naoyuki-oi.la.coocan.jp/Research/CIE_2007_proceeding.pdf|first=Naoyuki|last=Oi|author2=Hironobu Takahashi|title=Preferred Combinations Between Illuminance and Color Temperature in Several Settings for Daily Living Activities|institution=Kyushu University|year=2007}}</ref> Individuals did prefer color temperature–illuminance pairs within the comfortable region for [[Eating|dining]], [[Socialization|socializing]] and [[Study skills|studying]], but also preferred color temperature–illuminance pairs that were in the lower uncomfortable region for night time activities and preparing for bed. This is linked to the Purkinje effect; individuals who desire some light at night time desire lower (redder) color temperatures even if luminance levels are very low.

Kruithof's findings may also vary as a function of [[culture]] or [[Geography|geographic]] location. Desirable sources are based on an individual's previous experiences of perceiving color, and as different regions of the world may have their own lighting standards, each culture would likely have its own acceptable light sources.

The illuminance of a source is the dominating factor for deciding as to whether or not a source is pleasing or comfortable, as viewers participating in this experiment evaluated a range of correlated color temperatures and illuminance levels, yet their impressions remained generally unchanged as correlated color temperature changed.<ref>{{cite journal|last=Bodmann|first=H.W.|author2=G. Sollner |author3=E. Voit |title=Evaluation of lighting level with various kinds of light|journal=Proceedings of the CIE|year=1963|volume=15}}</ref> Additionally, there is a relationship between correlated color temperature and apparent brightness of a source.<ref>{{cite thesis|last=Han|first=S.|title=Effect of Illuminance, CCT and Decor on the Perception of Lighting|degree=M.S.|location=[[Troy, New York]]|institution = [[Rensselaer Polytechnic Institute]]}}</ref> From these findings, it is evident that color rendering index, in place of correlated color temperature, may be a more appropriate metric for determining as to whether or not a certain source is considered pleasing.