A light source (25) for emitting collimated light (29) in particular for a large area luminaire (21) comprises a light guide unit (43) optionally comprising a plurality of light guide strips (91) configured for guiding light received at the at least one lateral coupling face (47), for example, by total internal reflection. The light guide strips comprise a plurality of localized light source regions (57) at a main front face (55A) for having light pass there through, wherein the light source regions (57) are provided along the light guide strip (91) within a non-source region (59). The light source (25) further comprising a plurality of light emitting units (41) for emitting light into the light guide strips (91) through respective portions of the at least one coupling face (47), and a collimation unit (45) extending along the main front face (55A) and comprising a plurality of collimating elements. Each collimating element, which may be a compound parabolic concentrator or TIR lens, comprises an input side and an output side, is optically associated to one of the plurality of light source regions (57), and is configured to receive light emerging from the associated light source region (57) at its input side and to emit collimated light (29) from a respective collimated light emitting region (61) formed at its output side. In another embodiment the light emitting units are configured to emit primary light having a spectral distribution that compensates for spectral losses accumulated by the primary light while propagating within the light guide unit. In a further embodimentthe collimated light has a direction that is tilted with respect to the normal to a light emitting face of the light source. In an additional embodiment the ration of the area of the plurality of light source regions with respect to the area of the main front face and/or the area of the non-source region is less than or equal to 20%. In a further embodiment a plurality of reflective structures isassociated with the light source regions.