EFFECTS OF SPECTRAL MODIFICATION ON PERCEIVED BRIGHTNESS AND COLOR DISCRIMINATION
Open Access
- Author:
- Wei, Minchen
- Graduate Program:
- Architectural Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Kevin William Houser, Thesis Advisor/Co-Advisor
Kevin William Houser, Thesis Advisor/Co-Advisor - Keywords:
- Spectral Modification
Perceived Brightness
Color Discrimination - Abstract:
- This study characterized the effect of spectral modification on perceived brightness and color discrimination under illumination provided by a pair of 32W, 4-foot, linear fluorescent lamps: SPX 3000K (SPK3K) and the Reveal® linear fluorescent (RevLF). Sixty subjects participated, with half 25 years or younger (mean = 22.5, std. dev. = 1.7) and half 60 years or older (mean = 81.4, std. dev. = 7.1). The side-by-side evaluation mode was employed to characterize perceived brightness. Subjects made a forced choice for each of 44 pairs of light settings that: were practice trials (4 pairs); differed in spectrum at equal illuminance (8 pairs); varied in both spectrum and illuminance (24 pairs); or were identical (i.e. null condition trials, 8 pairs). Light settings were set within a range of 240 to 330 lux and the rooms had neutral gray surfaces. Equal perceived brightness was inferred from the paired comparisons, and found to occur when the photopic quantity (e.g. illuminance, luminance) from the RevLF was 5% lower (younger subjects) or 8% lower (older subjects) than that provided by the SPX3K lamps. At equal illuminance of 330 lux, the room illuminated by the RevLF was preferred to the one illuminated by the SPX3K by 67% of the younger subjects and 73% of the older subjects. Color and brightness were most commonly cited as reasons for preference. Color discrimination was characterized under 300 lux of RevLF and SPX3K illumination using the Farnsworth-Munsell 100 Hue Test (FM-100). For color-normal people below 25 years of age, and for those above 60 years of age who had cataract surgery, the red-green partial error score was statistically better under RevLF illumination. A significant difference was not found in the blue-yellow partial error score or in the total error score. When brightness perception is considered in isolation, the spectral advantages of the RevLF cannot be offset by the disadvantage of lower luminous efficacy. That is, these data suggest that at equal brightness a room illuminated with RevLF will consume more energy than an otherwise identical room illuminated with SPX3K. When brightness and color discrimination are considered together, as with visual clarity, it is unknown whether RevLF or SPX3K illumination would be more energy efficient. Color discrimination, brightness perception, and overall preference all play a role in occupants’ gestalt evaluation, contribute to high performance building interiors, and play a role in sustainable lighting solutions designed to address occupant needs.