We know LED is a very long life semiconductor device,indeed it is subject to the ideal condition,especial for the temperature only when their heat transmission timely,.under this condition.that means,” radiating:will be a bottleneck for the LED lamp,or you can say ,”Heat” is the critical defect for one led lamp.
Therefore,good heat dissipation is an most important factor decide the lamp’s life ( besides,driver will be refer later) Further more,another three important measurements of white light quality are correlated color temperature (CCT). color rendering index (CRI) and Luminous (Lumen) output. many CFL lamps, quartz metal halide lamps, and some cool white fluorescent fixtures sufficient for the vast majority of applications. CCT describes whether white light appears warm (reddish), neutral, or cool (bluish). The standard definitions of CCT allow a range of variation in color that can be readily discerned by viewers even when the CCT value is the same. Ensuring color consistency, therefore, is a major concern of LED manufacturers. Leading LED lighting manufacturers use various LED selection schemes (binning) to ensure color consistency from fixture to fixture.
On a scale of 0 (worst) to 100 (best), CRI measures the ability of a light source to reproduce the colors of objects faithfully in reference to an ideal light source — the sun, for example, or an incandescent lamp. Most office, retail, educational, medical, and residential spaces require a minimum CRI of 70 – 90. Many white-light LED lighting fixtures available today achieve CRIs of 80 or better, comparable to mings of the standard CRI test for LED lighting, some LED lighting fixtures with low CRI scores produce visually pleasing light that renders colors appropriately. Color Quality Scale (CQS), a color-rendering standard that better accounts for the unique properties of LED light sources, is currently under development. Until CQS or a similar alternative is in place, you should observe LED sources with low CRI scores in person to evaluate how well they render color.
For the luminous,at this moment ,it is to reach 130-140Lumen/watt per LED,some can reach 200 lumen for CREE,Philips,Osram Power LED. But for 1 complete lamp,most of them only reach 75lumen/watt for LED downlight,LED spotlight, But for another like LED tubes, LED street light,not hard to reach 900-100Lumen/Watt .This is an complicated items for the whole efficiency, as many factors to affect.