principles, definitions 005 e l m a r c o Lighting is an integral part of the environment in which we live, work, rest. Safety and efficiency of work as well as relaxation and good mood – all of these depend on quality of lighting. The quality of lighting must simultaneously take into account three aspects: h u m a n n e e d s , e c o n o m i c c o n d i t i o n s , a r c h i t e c t u r a l s t a n d a r d s . Fulfilment with all the requirements of proper lighting is difficult, but it should be striven to meet the widest possible range of conditions. In order to discuss the impor- tance of the mentioned aspects further, the most important parameters of light have been presented in an abbreviated form. H U M A N N E E D S visibility health c omfort action capability E C O N O M Y cost of investment cost of operation long operational life energy consumption environmental impact A R C H I T E C T U R E form composition style meeting standards Uniform distribution of luminance Reduction of direct and reflective glare Proper colour rendering Proper shading in the interiors Proper light colour and colouring Proper direction of light Safe lighting Aesthetics and harmony of integration into the surroundings Energy-efficient lighting Required level of lighting intensity at working planes P R I N C I P L E S O F G O O D L I G H T I N G L u m i n o u s f l u x ∅ (Lm) is the total amount of light emitted from a light source. L i g h t i n t e n s i t y I (cd) determines the amount of light emitted in a particular direction. This is an angular density of luminous flux. By means of luminous intensity, curses of light distribution for a particular fixture are formed. L i g h t i n g e m i t t a n c e E (lx) the amount of light which – when sent from a fixture –reaches an illuminated surface. L u m i n a n c e L (cd/m 2 ) is the light which bounces back from the surface and reaches the ob- server's eye. (Luminance is everything we see). Also, a light source has got its luminance as light is always emitted from a particular surface, sometimes very small, then this is high- value luminance which dazzles the observer’s eyes. This is so-called the phenomenon of glare. L i g h t c u r v e is a surface formed by a set of points beings ends of light vectors "hooked" in the central part of a fixture. "Vector length" – a particular value of luminosity. A position of vectors in space correspond to a direction at which luminosity occurs. Otherwise, this is a curve set in polar or rectangular coordinates presenting the relation of luminosity from an angle of light beam. C o l o u r r e n d e r i n g i n d e x ( R a ) is a measure determining the characteristics of colour rendering in a particular light. The maximum value is 100 and it is set for sunlight (100–80 very good, 80–60 good, 60–40 fair). C o l o u r t e m p e r a t e expressed in Kelvin determines the colour of emitted light. Temperature of cold day light is set at 6500 0 K, for a candle – 1800 0 K, for a light bulb – 2700 0 K. C o n t r a s t K is the difference in appearance of two parts of the field of view simultaneously viewed one after the other. It is determined by the difference of luminance referred to base luminance [K=(L 2 -L 1 )/L 1 ], or as a ratio of luminance [K=(L 2 /L 1 ]. There is a luminance contrast and colour contrast. U n i f o r m i t y o f l i g h t e m i t t a n c e δ is the ratio of the minimum light emittance to average light emittance within the considered area. δ =E min /E śr sometimes δ =E min /E max U n i f o r m i t y o f l u m i n a n c e δ is the ratio of minimum luminance to average luminance. δ =L min /L śr sometimes δ =L min /L max Applied outdoors Colour rendering Applied indoors V E R Y G O O D 100–90 V E R Y G O O D V E R Y G O O D 80 G O O D G O O D 70–60 S A T I S F A C T O R Y S A T I S F A C T O R Y 40 U N S A T I S F A C T O R Y C o l o u r a p p e a r a n c e g r o u p s C O L O U R A P P E A R A N C E C O L O U R T E M P E R A T U R E warm below 3300 0 K intermediate (white) from 3300 0 K to 5300 0 K cold (daytime) above 5300 0 K S e l e c t i o n of the right lighting fulfilling all the requirements of projected effects, energy efficiency and sustainability is a complex task which should be entrusted to professionals. However, we would like to familiarise you with basic information on lighting and our range of products in order to find "common ground" and meet your expectations as our customer. L i g h t c o n e is a solid plot with marked maximal and average values of lighting emittance occurring at horizontal profile areas variously distanced from a fixture. P o l a r p l o t illustrates the distribution of lighting emittance in a transverse plane (0 0 –180 0 ) and longitudinal plane (90 0 –270 0 ) with respect to the position of a light source. l u m i n o u s f l u x in lm l u m i n a n c e i n cd/m 2 l u m i n o s i t y in cd l i g h t i n t e n s i t y in lux D EFIN ITIO N S L I G H T I N G Q U A L I T Y 00_wstep_Layout 1 2022-01-09 16:47 Page 5