Final (Lectures 17-26) Flashcards
(45 cards)
Primary Colors
Red, yellow, and blue
Trichromatic Theory (timeline)
1802: Young postulates the existence of three receptors
1850: von Helmholtz describes these as short preferring, middle preferring, and long preferring
1956: Svaetichin identifies cells in the eye sensitive to three different wavelengths
Opponent Process Theory
19th century: Herin postulated three color pairings: blue/yellow, red/green, black/white
Explains afterimages and why we don’t see colors such as reddish green and yellowish blue
Modern Synthesis of Color Recognition
- Trichromatic stage: trichromatic cone cells respond positively to one of the three frequencies exhibited by the photons arriving on their surface
- Opponent process stage: the three color channels are discovered by nearby opponent cells, opponent cells tuned to luminosity are excited by the red, green, and blue color signals, the Cg cells are excited by red and blue and inhibited by green, and the Cb cells are excited by red and green and inhibited by blue
Types of Colorblindness
Anomalous trichromats: 3 photopigments but only form 2 groups
Dichromats: missing 1 photopigment entirely
Hue
Variation in wavelength or spectral distribution
Due to the wavelength of light
What most people probably mean when they say color in everyday language
Value
Brightness
Intensity ranging from totally dark black to luminous white
Chroma
Purity (amount of white) added represented in a color solid
Also called saturation
Vividness or dullness of a color
LAB Color Space
L: luminance(0: black, 100: white)
a: red to green (-:green, +: red)
b: blue to yellow (-:blue, +:yellow)
Specular Reflectance
Mirror-like, images are preserved
Diffuse Reflectance
Shiny but no clear images
Illuminant
Theoretical source of visible light and its spectral power distribution
Requirements of Color Sensations
Perception - requires a light source, modified, and detector
QDA
Panel generates its own terms during discussion
Panel leader facilitates but is non-directing
Panelists work independently for formal evaluations
Data are typically displayed in radar plots
Spectrum
Universal intensity references
Panel leader can be influential
Extensive training
F value
MStreatment:MSerror
ANOVA Interactions
Product by replicates
Product by panelists
Panelist by replicates
Completed Block Design
All panelists taste all products
Reasons for an affective test
Following a significant discrimination result
Pre-market blind labeling testing
New product prototype testing
Line extensions
Advantages and disadvantages of a line or visual analog scale
A: analyze with traditional parametric statistics, easy for subjects to use, avoids issues of label spacing
D: more work to score, end use avoidance,, anchor discrepancies
Advantages and disadvantages of a hedonic gLMS
A: gets subjects to rate items outside of a narrow food context, generates ratio data,good for comparison across panelists
D: may not be the best choice for product oriented testing
Advantages and disadvantages of JAR scales
A: currently popular, unfolds acceptance scale, gives reasons for liking/disliking, gives immediate feedback
D: gives immediate feedback, requires directed attribute, potentially conflicting information, centering bias
Food Action Rating Scale
Behavior based scaling of attitudes toward product
Appropriateness scales
Measures a food or product in a situation
