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Light Intensity Measurements in Poultry Houses


Light intensity is an important management factor for breeder type poultry. There is evidence suggesting a minimal threshold intensity to obtain optimal reproduction performance. Most poultry managers use the conventional light meter (photometer) when attempting to ascertain light intensity (footcandles or lux) in a house or when trying to equalize intensity among several houses. This is acceptable when only one type of lamp is used to provide supplemental light. However, more than one type of artificial light source may be used in current light management practices. The photometer has limitations in these situations. Light intensity measurement by the light meter is not accurate when comparing different light sources.

The photometer, which displays intensity as footcandles, has a light receptor cell that perceives light with the same spectral intensity as the human eye. Maximum reception of light energy occurs at a wavelength of 555 nanometers (green light) and decreases to a minimum at the two extremes of the visible light spectrum (blue and red). This results in an uneven detection of the light energy measurement across the visible light spectrum.

The visible light spectra of supplemental light sources vary significantly from one another and thus the sensitivity of a photometer to these light sources is not the same. Absorption of photons is required for any light induced effect to occur and should be considered as a standard unit of measure for light intensity. This is especially true where light sources other than the incandescent lamp is used. The instrument required is more expensive than the photometer and will be impractical for most poultry operations. The measured intensity relationship within a light source between footcandles and photons is proportional and linear. Thus, a relationship between light intensity photons (M/sec/m2) and footcandles (fc) can be determined. If the poultryman is to achieve equalized intensity levels with different light sources, the most sensible unit to standardize light intensity measurements is the photon (M/sec/m2).

A correction factor to equate light intensities as M/sec/m2 per footcandle for each light source was arrived at by:

Correction Factor = (M/sec/m2 for source) / (fc for source)

The correction factor calculated for each light source is shown in Table 1.



Table 1.

Correction Factors for Various Light Sources to Equalize the Number of Photons from Footcandle Data.

Light Source

Photons per Footcandle*

120 Volt Incandescent


130 Volt Incandescent


High Pressure Sodium


Cool White Fluorescent


Cool White Deluxe Fluorescent


Warm White Fluorescent


Warm White Deluxe Fluorescent


Day Light Fluorescent


Vita Light Fluorescent


Biaxial Compact Fluorescent (2700K)




It becomes apparent that in a practical measurement situation where light intensity is equalized in footcandles for incandescent and any other alternative light source, a higher light intensity in photons (M/sec/m2) will be observed in the incandescent than any of the other light sources. If intensities are equalized in terms of footcandles, these results demonstrate that some of the energy efficient light sources can reduce actual light intensity in photon energy by approximately 50% if incandescent light sources are replaced.

To replace one light source with another and still maintain the same light intensity as photons, a correction factor for a specific light source (Table 1) can be utilized in an algebraic expression to determine the needed light intensity. In determining the desired light intensity, us the following equation with the information in Table 1:

fc needed for NLS = (fc of CLS) (CF of CLS) / (CF of NLS)


NLS = New Light Source

CLS = Current Light Source

CF = Correction Factor

fc = Footcandle



When controlled environmental housing is used in conjunction with low intensity lighting, it is critical that at least the minimal threshold light intensity be attained. There is no conclusive evidence for an absolute threshold intensity. It is suggested that one maintain an intensity of two to five footcandles. Using different light sources will require attention to the measurement of the light intensity in the poultry house when making comparisons between houses. When different light sources are used. This method to standardize light intensity values will be valuable to breeder managers to accommodate wavelength bias of the light meter associated with different light sources.




  1. General Electric Lighting Application Bulletin 905-61701R.

  2. Pyrzak, R., N. Snapir, G. Goodman and M. Perek. 1987. "The Effect of Light Wavelength on the Production and Quality of Eggs of the Domestic Fowl." Theriogenology 28:947-960.

  3. Pyrzak, R., T. D. Diopes. 1986. "Effect of Light Quality on Egg Production of Caged Turkey Hens." Poultry Science 65:199-200.

  4. Pyrzak, R., N. Snapir, G. Goodman, E. Arnon, M. Perek. 1986. "The Influence of Light Quality on Initiation of Egg Laying by Hens." Poultry Science 65:190-193.

  5. Wineland, M. J. and T. D. Siopes. 1992. "Light Intensity Measurements of Different Light Sources." Journal of Applied Poultry Research In Press.


Prepared by Michael J. Wineland, Extension Poultry Specialist, and Tom D. Siopes, Professor of Physiology
North Carolina State University
11/92 PS Facts #17


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