How to Correct for Spectral Errors of Popular Light Sources - Prior to June 1, 2021

NOTE: The Original Quantum Series spectral response has changed as of June 1, 2021. The new model numbers are denoted with an "X". Below, you will find the Original Quantum spectral errors. To access Original X Quantum spectral errors, please click here >

Apogee quantum sensors accurately quantify the amount of photosynthetic light striking a surface in units of µmol m-2 s-1. There are, however, certain factors that can introduce varying small errors into these measurements. One of these factors, spectral error, occurs when measuring a light source that has a different spectral output than the light used to calibrate the sensor. This error occurs because no quantum sensor can perfectly match the ideal quantum response, which is defined as an equal response to all wavelengths of light between 400 and 700 nm. When measuring certain light sources with our quantum sensors, an even higher level of accuracy can be achieved by applying post-measurement correction factors according to the chart below.

Spectral errors can be approximated using wavelength dependent calculations that account for the spectral response of the quantum sensor, the spectral output of calibration light source, and the spectral output of light source being measured. The table below displays the calculated theoretical spectral errors and corresponding correction factors for many different popular lights sources. The spectral errors are calculated relative to each sensor's calibration source (the SQ-110 is calibrated to clear-sky sunlight, the SQ-120 and SQ-500 are calibrated to 4100K cool white fluorescent T5 lamps).

To correct for spectral error multiply your measured value by the correction factor (CF) associated with your light source. For example, if you are using an SQ-120 under a Blue LED (448nm), which has a spectral error of -12.7 and a CF of 1.15, and you measured 115 µmol m-2 s-1, you would multiply your measurement of 115 µmol m-2 s-1 by the CF 1.15 to get 132.3 µmol m-2 s-1 (115 x 1.15 = 132.3).

SQ-110 correction factors apply to sun calibrated models SQ-110, 212, 214, and 215, and models SQ-420, MQ-100, 200, and 210 when in SUN setting.

SQ-120 correction factors apply to electric calibrated models SQ-120, 222, 224, and 225, and models SQ-420, MQ-100, 200, and 210 when in ELEC setting.

SQ-500 correction factors apply to models SQ-500 and 520, and MQ-500, 501, and 510.

This information is also available as an interactive tool, which allows users to upload their own lighting spectrum.

Light SourceSpectral Graph
(Click to Enlarge)

Spectral Error
SQ-110
(SUN)

Correction Factor
SQ-110
(SUN)

Spectral Error
SQ-120
(ELEC)

Correction Factor
SQ-120
(ELEC)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

Agro Ceramic Metal Halide 0.0 1.00 -16.3 1.19 -1.8 1.02
Apache W LED 15.8 0.86 -0.8 1.01 -0.5 1.01
Blue LED (448nm) 4.2 0.96 -12.7 1.15 0.8 0.99
CF GE 45 W 16.6 0.86 -0.5 1.01 -0.9 1.01
CF Sylvania 30 W 12.3 0.89 -3.8 1.04 0.0 1.00
CWF T5 Sylvania 16.9 0.86 0.0 N/A 0.0 N/A
Light Source Spectral Graph
(Click to Enlarge)

Spectral Error
SQ-110
(SUN)

Correction Factor
SQ-110
(SUN)

Spectral Error
SQ-120
(ELEC)

Correction Factor
SQ-120
(ELEC)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

CWF T8 Sylvania 16.6 0.86 -0.5 1.01 0.2 1.00
CWF T12 Sylvania 15.5 0.87 -1.6 1.02 0.3 1.00
Flip Ceramic Metal Halide 10.9 0.91 -14.6 1.17 -0.3 1.00
Green LED 524nm 24.9 0.80 7.0 0.93 3.0 0.97
High Pressure Sodium 17.7 0.85 0.5 1.00 0.0 1.00
Illumitex RB LED -36.0 1.56 -45.2 1.82 -2.6 1.03
Light Source Spectral Graph
(Click to Enlarge)

Spectral Error
SQ-110
(SUN)

Correction Factor
SQ-110
(SUN)

Spectral Error
SQ-120
(ELEC)

Correction Factor
SQ-120
(ELEC)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

Incandescent 40 W -15.8 1.19 -28.5 1.40 -7.3 1.08
Incandescent 100 W -17.0 1.20 -29.5 1.42 -7.6 1.08
Kessil Tuna Blue 11.9 0.89 -4.7 1.05 1.7 0.98
LI 1800-02 Calibrator -10.6 1.12 -24.1 1.32 -5.7 1.06
Lighting Science RB LED -48.4 1.94 -55.8 2.26 -3.4 1.04
Lighting Science RW LED -43.4 1.77 -51.5 2.06 -3.0 1.03
Light Source Spectral Graph
(Click to Enlarge)

Spectral Error
SQ-110
(SUN)

Correction Factor
SQ-110
(SUN)

Spectral Error
SQ-120
(ELEC)

Correction Factor
SQ-120
(ELEC)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

Metal Halide 13.2 0.88 -4.3 1.04 -5.7 1.06
Quartz Halogen -10.5 1.12 -24.0 1.32 -5.7 1.06
RB LED 19.3 0.84 2.2 0.98 -1.5 1.02
Red LED 635 nm 21.7 0.82 -4.4 1.05 -2.0 1.02
Reflected Conifer 5.5 0.95 -11.3 1.13 -2.2 1.02
Reflected Deciduous 4.9 0.95 -11.9 1.14 -2.0 1.02
Light Source Spectral Graph
(Click to Enlarge)

Spectral Error
SQ-110
(SUN)

Correction Factor
SQ-110
(SUN)

Spectral Error
SQ-120
(ELEC)

Correction Factor
SQ-120
(ELEC)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

Reflected Grass 5.7 0.95 -10.9 1.12 -2.2 1.02
RGB LED 20.3 0.83 3.0 0.97 -0.8 1.01
Sun Clear 0.0 N/A -14.8 1.17 -2.2 1.02
Sun Cloudy 1.4 0.99 -14.4 1.17 -1.7 1.02
Under Alfalfa Canopy 6.4 0.94 -11.9 1.14 -1.7 1.02
Under Maple Canopy 6.8 0.94 -11.8 1.13 -0.9 1.01
Light Source Spectral Graph
(Click to Enlarge)

Spectral Error
SQ-110
(SUN)

Correction Factor
SQ-110
(SUN)

Spectral Error
SQ-120
(ELEC)

Correction Factor
SQ-120
(ELEC)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

Under Pine Canopy 5.3 0.95 -12.9 1.15 -0.4 1.00
Under Wheat Canopy 6.4 0.94 -11.7 1.15 -1.1 1.01
Valoya RW LED -16.0 1.19 -28.0 1.39 -6.0 1.06
WWF LED 6.0 0.94 -9.2 1.10 -1.9 1.02
2 Actinic, 2 Blue Plus -2.3 1.02 -16.8 1.20 -3.0 1.03
3 T5, 1 Actinic 9.2 0.92 -7.0 1.08 -2.0 1.02
4 Actinic -16.0 1.19 -28.5 1.40 -10.0 1.11
4 Blue Plus 7.4 0.93 -8.5 1.09 -3.0 1.03