An edge-lit backlight, comprising: a front and back reflector (12, 14; 34) forming a hollow light recycling cavity having a cavity depth H, wherein the front reflector is partially transmissive and provides an output region of area A out, and wherein the cavity depth H is the physical distance from the back reflector to the front reflector along an axis perpendicular to the output region or in the case in which the output area and the back reflector are non-planar, H is the average separation between the output area and the back reflector; and n light sources (24a, 32b,), where n ≥ 1, disposed proximate the periphery of the backlight, so as to emit light into the light recycling cavity, the light sources having an average plan view source separation parameter SEP and collectively having an active emitting area parameter A emit, wherein SEP is a measure of the degree to which the light sources (24a, 32b) are disposed in a uniform spatial distribution within the cavity relative to the output region and in the case, in which the back reflector has transverse dimensions of length L in the x-direction and width W in the y-direction, which is orthogonal to the x-direction, the associated front reflector and output region have the same transverse dimensions and are co-extensive with the back reflector (14, 34) and the light sources are arranged in a substantially regular repeating pattern to form one column running along the y-direction, SEP is defined by: SEP = 1⁄2 (L/1+W/n); and further wherein A emit is the total area of all the light-emitting surfaces of the n light sources; wherein a parameter A equals A emit /A out; and wherein a parameter B equals SEP/H; characterized by the parameter A being in a range from 0.0001 to 0.1, and parameter B being in a range from 3 to 10. a front and back reflector (12, 14; 34) forming a hollow light recycling cavity having a cavity depth H, wherein the front reflector is partially transmissive and provides an output region of area A out, and wherein the cavity depth H is the physical distance from the back reflector to the front reflector along an axis perpendicular to the output region or in the case in which the output area and the back reflector are non-planar, H is the average separation between the output area and the back reflector; and n light sources (24a, 32b,), where n ≥ 1, disposed proximate the periphery of the backlight, so as to emit light into the light recycling cavity, the light sources having an average plan view source separation parameter SEP and collectively having an active emitting area parameter A emit, wherein SEP is a measure of the degree to which the light sources (24a, 32b) are disposed in a uniform spatial distribution within the cavity relative to the output region and in the case, in which the back reflector has transverse dimensions of length L in the x-direction and width W in the y-direction, which is orthogonal to the x-direction, the associated front reflector and output region have the same transverse dimensions and are co-extensive with the back reflector (14, 34) and the light sources are arranged in a substantially regular repeating pattern to form one column running along the y-direction, SEP is defined by: SEP = 1⁄2 (L/1+W/n); and further wherein A emit is the total area of all the light-emitting surfaces of the n light sources; wherein a parameter A equals A emit /A out; and wherein a parameter B equals SEP/H; characterized by the parameter A being in a range from 0.0001 to 0.1, and parameter B being in a range from 3 to 10.