Lighting Considerations for Photorealism
Promis.e 's advanced photo-realistic rendering lets you produce lifelike images of your models. You can use IES lighting data files to provide the most accurate lighting, but, you can use the standard light source cells as well, to provide the illumination. With standard light source cells, both processes use the Lumens value, multiplied by the Bulbs value, to determine the brightness of the light source. Thus, you can set the correct Lumens value for a single bulb of the light source and then use the Bulbs setting to quickly change its brightness, if required.
Where correct lighting effects are required, it is recommended that you work with IES lighting data files.