Light intensity is much mis-understood because of the adapatbility of the human eye to a range of lighting conditions. By contrast, direct sunlight provides at least 8000 lux. Light Sources Sunlight is probably the best type of light that you can give your plants for healthy growth, good leaf colour and flowering. Plants have evolved and adapted to the natural light found in their habitat. The quality, intensity and duration of the light in a plant's habitat provides a baseline for the provision of artificial light supplements in other climates.
Natural sunlight has the great advantage of being free, and generates no greenhouse gases.
However, the quantity of sunlight on offer depends on the vagaries of climate, lattitude and time of year. The day length affects the initiation of flowering for many plants such as Christmas Cacti, but is out of the grower's control unless supplemental lighting or light exclusion is used. Another negative aspect of sunlight is that a sudden burst of sunshine after the dark winter months can lead to scorch and scarring of plant bodies. This can largely be obviated by timely use of shading. Tungsten halide lamps produce a clean white light at a colour temperature of about 3500 o C extending into the blue and ultra-violet part of the spectrum.