Lighting_Fundamentals

When selecting any lamp it's important to have a basic understanding of how both the quality and quantities of the selection not only enhances the ability for us to see, but how much energy does it take to accomplish this task. In the charts below you will see comparisons of different lamps and their comparative efficiencies. For plant lighting, higher lamp efficiencies, within the proper spectrums, means less operating costs by lowered wattages, lower heat generation by the lamp/ballast, maximum canopy penetration, long lamp life and minimum lumen depreciation will all contribute to successful grows.
How People See Light For human vision we design lighting levels with two distinct kinds of lumen output. The first is called Photopic or Design Lumens, which represents the relative sensitivity of the eye under intense lighting such as daytime cloudless outdoor sun conditions. Photopic lumen output is registered by the cones in the human eye and is measured in Lumen, Lux and Foot Candles. The second type of lumens are called Scotopic, which represent the sensitivity of the eye under typical interior or night lighting conditions and cannot be measured directly with a standard light meter. Scotopic lumen output is registered by the rods of the human eye and also controls pupil size directly effecting visual acuity for given task levels.
Measuring Light, Energy and Efficiencies Below we show how different light sources Design Lumen readings compare when read by a standard light meter and measured in Conventional Photopic Lumen values. For lighting design that wishes to maximize energy efficiencies by specifying light sources with both high Scotopic and Photopic Lumens, a Correction Factor (S&P Ratio) must be applied to the Photopic Lumen per Watt readings. When applying this correction factor you will notice drastically different usable light outputs as measured in Pupil Lumen per Watt. Higher Pupil Lumens per Watt will significantly reduce the amount of energy necessary to satisfy maximum visual acuity within the optimal yellow-green regions of the spectrum. In other words; the higher the Pupil Lumen/Watt the less energy will be required of the lamp for the eye to accurately see what it's observing. To illustrate this you can see by the charts below that the LPS (Ugly Yellow Street Lighting) lamp is more efficient from a conventional efficacy (Lm/W) perspective. However the LPS has a very low S/P ratio and poor pupil lumens per watt when compared to induction. Now the CRI and the VEL would indicate poor visual acuity. What this means is that while there may be a high lumen per watt when using LPS, the ability to accurately gauge the color of what we are observing is extremely poor.
Measuring Energy Efficiency Design Lumens
Lamp Type	Conventional Lumens per Watt	Correction Factor (S&P Ratio)	Pupil Lumens per Watt
Induction Lamp (5000K)	85	1.96	166.6
Metal Halide	85	1.49	126
Warm White Fluorescent (2900K)	65	0.98	64
Low-Pressure Sodium	165	0.38	63
High Pressure Sodium (50W)	65	0.76	49
LED (5000K)	20	2	40
Deluxe Mercury Vapor	40	0.86	34
Tungsten Halogen	22	1.32	29
Standard Incandescent	15	1.26	19

Induction Lamps: Why They Appear Brighter Below we show how Photopic and Scotopic Values vary between different lamp types and how bright they will then appear to the eye. This is known as Apparent Brightness and is not measured in the conventional Lumens, Lux or Foot-candle readings. There are a number of terms engineers use that reference Apparent Brightness; Visually Effective Lumens (VEL), Spectrally Effective Lumens (SEL) or Pupil Lumens as this measurement, but whatever phrase you use, they all refer to the same thing: Apparent Brightness.
Apparent Brightness
Type	Wattage	Photopic Value	Scotopic Value	VEL
Induction	100 w	9,625	19,250	16,527
	200 w	20,500	41,000	35,201
	250 w	27,200	54,400	46,706
	400 w	54,090	108,180	92,883
High Pressure Sodium	150 w	11,250	8,550	9,082
	250 w	22,100	16,796	17,841
	400 w	36,000	27,360	29,063
	1000 w	90,000	68,400	72,630
Metal Halide (Pulse Start)	150 w	8,000	11,920	10,919
	250 w	15,000	22,350	20,473
	400 w	28,000	41,720	38,216
	1000 w	93,000	138,570	126,940

Standard Units of Measurement for Vision When taking into account the standard photometric measurements of light for human vision the system of units we measure would be the LUMEN, it measures the total amount of light emitted from a source. This light is then distributed over an area and the illuminated area is measured in LUX. LUX is measurement of intensity as perceived by the human eye. It is a way of measuring how many LUMENS fall within a square meter of an illuminated surface. The difference between the LUX and the LUMEN is that a LUX measures the area over which the LUMEN is distributed. These levels are inversely proportional to the area being lit. The larger the area the lower the intensity of the LUX levels. For example a reading of 1000 LUMENS would correlate to 1000 LUX at a 1 meter area however the LUX illumination levels would fall to 100 LUX over a 10 meter area. In the United States you'll often hear light measurements in FOOT-CANDLES. This term is used considerably in construction related projects and by engineers who deal with US Standards of measurement. LUX and FOOT-CANDLES are different units of the same quantity in that FOOT-CANDLE will measure the amount of LUMEN PER SQUARE FOOT whereas LUX measures the LUMEN PER SQUARE METER. Other then in the United States you will not usually hear light measured in FOOT-CANDLES. Since all light is emitted in wavelengths, and we know that the human eye can see certain wavelengths better then others, with the peak being measured @ 555 nanometers, we can now determine a given lamps source LUMENS PER WATT (LPW). The LPW measurement adjusts for the spectral wavelengths the lamp produces. So when determining a task level of illumination for human eyesight, we can decide which lamp will best suit the task for the least amount of wattage, with factored depreciation, and how important the color, as measured in the Color Rendering Index (CRI), to best match the task.
Measuring Induction Lighting Efficiencies Induction lighting systems surpass traditional HID lighting systems in the combined CRI and the Scotopic/Photopic (S/P) Ratios. Of the wide variety of energy efficient lamp choices on the market today Inda-Gro Induction Grow Lighting more closely represents natural sunlight and provides the highest VEL Lm/w while still peaking in the 380 and 720 nanometer ranges. Additionally our grow lights, with ballast efficiencies of 95%, have demonstrated to best imitate the advantages of the higher wattage HID lamps while saving up to 70% less wattage per fixture.