56|CUADERNOS L is the luminance of the luminous parts of each luminaire in the direction of the observer’s eye. ω is the solid angle (sa) of the luminous parts of each luminaire on the eye of the observer. p is the position index of Guth, it is a table of tabulated data that assigns a value to every position of the observer inside the installation. Summary The most important conclusion obtained from these small calculations is that estimating adequately the luminous area of the luminaires for interior lighting is very important in order to convey an accurate and suitable data of the glare of an installation. To create a good lighting project, specially in work places, we have to adequate the luminous levels to the needs of the workers, have a good index of color rendering and a comfortable and adequate lighting. An inadequate estimate of the glare degree of the installation can produce more problems than expected in determined work environments, such as accidents and health problems (continous headaches, itchy eyes, high sensitivity to light, etc.) It is essential to execute a good design of luminaires for an interior with attention to the degree of glare they produce, specially in places for working or studying. It is important to choose the most appropriate elements to be used in the luminaires with LED sources, because even though diffusing elements homogenize the light output, they also have a diffusive function that produces high levels of luminance in areas were it is not reccomended. The adequate use of optic elements in the design of this type of luminaire aid in making the most of products that can provide adequate and safe installations that allow us to perform our work without unwanted glare. It is important to remember that the unified glare rating depends on the luminaire itself and on the installation. A luminaire that is suitable for some installations is not necessarily suitable for others; every place has different demands. ■ Note: Work presented on the XL NATIONAL SYMPOSIUM OF LIGHTING (Málaga 28- 31 mayo 2014) “Estimating adequately the luminous area of the luminaires for interior lighting is very important in order to convey an accurate and suitable data of the glare of an installation”.