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Metamerism and Illuminants

Contents

Introduction •

What is Metamerism? •

Kinds of Metamerism •

Importance of in Metamerism •

What are Illuminants? •

What is the difference between a light source and an illuminant? •

Different Industrial Illuminants •

Colour Temperature •

Impact of Brightness and Position of the Light Source •

Use of Matching Cabinets •

Reducing the Effects of Metamerism •

Contact us about Metamerism and Illuminants • Bulletin Post quality isdefinedsuchasinastandard matchingcabinet. and properties colour the wheresource,'controlled' a being source light the on depends perception visual Accurate • • its affecting factor important most the is product a view appearance andinmetamerism.Thetwomajorfactorsthatinfluence whatweseeare: to observer the by used source light the of energy The The nextfewsectionswilldescribeilluminants. • • • Metamerism changesfrom oneviewingconditiontoother. Severalkindsofmetamerismexist: car itmaywellappeartobebrown undersodiumlighting.Thisphenomenonisknownasmetamerism. you park your bright car at the roadside in daylight. Darkness falls and although you would still say you have a red sourcelight the on depending vary to appear will object an example, of For colour it. The illuminate to used is which match underonelightsource, nolongermatchwhenviewedunderadifferent lightsource. whereto scientificphenomenon appear a colourwhich is common samples Metamerism acolour of two description and colourmatchingcabinetstoassesscolour. illuminants standard adopting by metamerism of effects the reduce can you how explain will bulletin technical This of condition the of because is This stage. metamerism. another at observed shade in difference a be might there distribution, Colour The supply materials. chain consists of many different various stages and whilst of a garment may pass mixturecolour matching at one stage a of the is product finished the matching allthesematerialsisimportanttomeettheneedsoffinalconsumer. where process, complex a is production Apparel specific colour atthedefinedtemperatures ofthelightsource, unit [K]. a with heat radiates that radiator temperature artificial an of distribution energy spectral the of measurement a are theoreticala is values illuminant illuminant An the sourceprofilegeneral, a In with published. light visible is of which What is Metamerism? Introduction What are Illuminants? Importance of Light in Metamerism Kinds of Metamerism Colour ofthebackground againstwhichanobjectisviewed The amountandqualityoflightilluminatinganobject the same(45degree) angletothelightsource Geometric Metamerism cannot alwaysbeavoided.Howeverbyproper selectionandtrainingofcolouriststheriskcanbereduced Metamerism Observer as adifferent colourunderadifferent illuminant Illuminant Metamerism is caused by a difference in colour vision between observers; it is highly subjective and subjective highly is it observers; between vision colour in difference a by caused is means an object may match under a certain illuminant to a certain observer, but appear can be controlled by viewing the samples at the same distance from the observer and at

Bulletin Post daylight daylight factories factories environments environments fluorescent light fluorescent generally seen in office generally seen in home resembling noon daylight resembling Commercial narrow band narrow Commercial , and , merchandisers and retailers; merchandisers Generally used in stores and Generally used in stores resembles north sky daylight resembles Cool fluorescent light, Cool white fluorescent Generally used in streets and Generally used in streets dyes and bleaches, resembles which simulates office or store which simulates office Usage / Kind of Illumination light, Incandescent or tungsten ; generally used by most Most commonly used illuminant tones look greyed and unnatural tones look greyed Used to evaluate colour quantity Common wide band fluorescent for rendering colours as it accents for rendering disadvantage is that it is very poor suppressing all red and makes skin all red suppressing Used to evaluate opaque materials, and uniformity, resembles noon sky resembles and uniformity, Reveals the presence of fluorescent Reveals the presence 70 50 93 92 94 85 93 85 62 100 CRI (Colour Rendering Index)

3000ºK 4100ºK 2100ºK 6500ºK 5000ºK 7500ºK 4100ºK 4150ºK 2856ºK 6500ºK Operating Temperature USA USA High High daylight daylight daylight halogen Daylight intensity intensity Tungsten European fluorescent fluorescent fluorescent fluorescent fluorescent fluorescent fluorescent 7 Phosphor 7 Phosphor 7 Phosphor commercial commercial commercial commercial commercial Lamp Type Vapour Sodium Mercury (INCA-A) Illuminant Fluorescent Fluorescent) (Cool White Illuminant A illuminant is the theoretical representation of the light source representation is the theoretical illuminant as a light source realised can be physically but not all illuminants as an illuminant, be specified can All light sources Illuminants have standard values which never vary, while the energy of a light source can vary can energy of a light source never vary, while the values which have standard Illuminants A light source is a physical emitter of radiation, such as a candle, a tungsten bulb and natural daylight, while an CIE Standard CIE Standard CIE Standard CIE Standard Designation High Pressure Illuminant UV Illuminant U30 Illuminant D75 Illuminant D50 Illuminant CWF Illuminant TL84 Different Industrial Illuminants Industrial Different What is the difference between a light source and an illuminant? illuminant? an and source light a between difference the is What • • • Note: CRI (Colour Rendering Index) is defined as the ability of the illuminant to render colours as they would appear under true daylight. true under appear would they as colours render to illuminant the of ability the as defined is Index) Rendering (Colour CRI Note: a perfect simulation of daylight. An index of 100 represents Bulletin Post Companies Book Stores Applications Classrooms, Mass Classrooms, Museums, Colour Matching Booths, Examination Areas, Conference Rooms, Conference Office Areas, Libraries Areas, Office Textile Industry, Printing Textile Merchandisers, Hospitals Merchandisers, Jewellery Shops, Medical Hotel Lobbies, Boutiques, Office Areas, Showrooms, Areas, Office Domestic tungsten lighting A Public Galleries Location Reception Restaurants Office Areas Office Appropriate Appropriate Alert Clean Inviting Moods Efficient Intimate Exacting Personal exclusive Effects & Effects colouration Non-threatening Store lighting Store TL84 Neat Bright Friendly Friendly Associated to Range Kelvin 6,500K 5,000K 4,100K 3,500K 3,000K Cool Warm Neutral Colour Daylight Artificial daylight Artificial CWX - Deluxe Cool White CWX - Deluxe White Warm WWX - Deluxe Saving ES - Energy Output HO - High CW - Standard Cool White Cool CW - Standard White Warm WW - Standard Temperature Colour Temperature Colour Light sources that have higher colour temperatures are 'warm' light sources. are temperatures 'cool' light sources, while those that have lower colour that quantifies the appearance of light. The terms ‘warm’ and ‘cool’ in lighting refer to subjective experiences, such as a warm flame or a cool winter sky. Colour temperature is a method for describing certain colour characteristics of light sources. It is a reference number is a It method is for a describing certain reference colour characteristics Colour temperature of light sources. • • • • • • D65 Applications of Colour Temperature Colour of Applications Cool and Warm Light Sources Light Warm and Cool Fluorescent Lamp Variants: Lamp Fluorescent Bulletin Post Cabinet Interior Dimensions Viewing Distance Viewing Backgrounds • • • • • appraisal withthebelowparameters: colour for used best are they and colour of assessment visual the for equipment standard the is cabinet matching A the objectsandangleofviewallaffect appearance. strikes light the which at angle the one, diffused large a or source small a from coming is illumination the Whether product. a of contrasts and colour parent the affects also illumination the of geometry The shadow. in seen be may that detail of amount the greater the and appear colours saturated more the illumination, the brighter the general, In shadows. in visible detail of amount the and colours of purity apparent the affects illumination of brightness The • • Use of Matching Cabinets Impact of Brightness and Position of the Light Source The wallarea behindthecabinetshouldbefinishedinlight emulsionBS00A01 to alevelof200300lux 'ArtificialDaylight' be should vicinity the in lighting general the and view of field the in be should directlights No Any windowsnearthecabinetshouldbefittedwithgrey blinds For bestresults, glare, extraneouslightsandanythingwhichwillmal-adaptthevisualresponse mustbeavoided The cabinetinteriorshouldbecoloured withMunsellGrey N5 of thesamples. Thesamplesshouldideallybe viewedata45ºangleofincidence tothelightsource regardlessconstant be also should viewed being samples the colour to the Matcher of Colour the of distance The The shadematchingcabinetutilises neutralgrey surroundings toaccommodatethe widestrangeofcolours Viewing Cavity Viewing Overall Area 1,520 mm 1,560 mm Width 560 mm 780 mm Height 590 mm 620 mm Depth Bulletin Post www.coatsindustrial.com Please and toconsiderusetheappropriate illuminantsandconditionsinmatchingcolour. dyestuff quality consistent use to important therefore is it textiles In object. coloured any of process manufacturing We have seen that metamerism and illuminants are important considerations in controlling and assessing colour in the Reducing the Effects of Metamerism contact yourlocalSalesOffice tofindoutmore aboutmetamerism andilluminants. September 2014