How to Correct for Spectral Errors of Popular Light Sources

NOTE: The Original Quantum Series spectral response has changed as of June 1, 2021. The new model numbers are denoted with an "X". To learn more click here.
To access Original 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-100X is calibrated to clear-sky sunlight, the 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-500 under a Blue LED (448nm), which has a spectral error of 0.8 and a CF of 0.99, and you measured 115 µmol m-2 s-1, you would multiply your measurement of 115 µmol m-2 s-1 by the CF 0.99 to get 113.85 µmol m-2 s-1 (115 x 0.99 = 133.85).

SQ-100X correction factors apply to models SQ-100X, 202X, 204X, and 205X, 420X, 421X, 422X, and MQ-100X, 200X, and 210X.

SQ-500 correction factors apply to models SQ-500, 512, 514, 515, 520, 521, 522, 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-100X
(Original)

Correction Factor
SQ-100X
(Original)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

Agro Ceramic Metal Halide Agro Ceramic Metal Halide Spectrum -0.9 1.01 -1.8 1.02
Apache W LED Apache W LED Spectrum Coming Soon Coming Soon -0.5 1.01
Blue LED (448nm) Blue LED (448nm) Spectrum 21.2 0.79 0.8 0.99
CF GE 45 W CF GE 45 W Spectrum Coming Soon Coming Soon -0.9 1.01
CF Sylvania 30 W CF Sylvania 30 W Spectrum Coming Soon Coming Soon 0.0 1.00
CWF T5 Sylvania CWF T5 Sylvania Spectrum 8.3 0.92 0.0 N/A
Light Source Spectral Graph
(Click to Enlarge)

Spectral Error
SQ-100X
(Original)

Correction Factor
SQ-100X
(Original)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

CWF T8 Sylvania CWF T8 Sylvania Spectrum Coming Soon Coming Soon 0.2 1.00
CWF T12 Sylvania CWF T12 Sylvania Spectrum 8.3 0.92 0.3 1.00
Flip Ceramic Metal Halide Flip Ceramic Metal Halide Spectrum -8.8 1.09 -0.3 1.00
Green LED 524nm Green LED 524nm Spectrum 29.6 0.70 3.0 0.97
High Pressure Sodium High Pressure Sodium Spectrum -0.7 1.01 0.0 1.00
Illumitex RB LED Illumitex RB LED Spectrum Coming Soon Coming Soon -2.6 1.03
Light Source Spectral Graph
(Click to Enlarge)

Spectral Error
SQ-100X
(Original)

Correction Factor
SQ-100X
(Original)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

Incandescent 40 W Incandescent 40 W Spectrum Coming Soon Coming Soon -7.3 1.08
Incandescent 100 W Incandescent 100 W Spectrum Coming Soon Coming Soon -7.6 1.08
Kessil Tuna Blue Kessil Tuna Blue Spectrum Coming Soon Coming Soon 1.7 0.98
LI 1800-02 Calibrator LI 1800-02 Calibrator Spectrum Coming Soon Coming Soon -5.7 1.06
Lighting Science RB LED Lighting Science RB LED Spectrum Coming Soon Coming Soon -3.4 1.04
Lighting Science RW LED Lighting Science RW LED Spectrum Coming Soon Coming Soon -3.0 1.03
Light Source Spectral Graph
(Click to Enlarge)

Spectral Error
SQ-100X
(Original)

Correction Factor
SQ-100X
(Original)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

Metal Halide Metal Halide Spectrum 8.7 0.91 -5.7 1.06
Quartz Halogen Quartz Halogen Spectrum -16.0 1.16 -5.7 1.06
RB LED RB LED Spectrum -21.2 1.21 -1.5 1.02
Red LED 635 nm RED LED 635nm Spectrum -30.9 1.31 -2.0 1.02
Reflected Conifer Reflected Conifer Spectrum 7.3 0.93 -2.2 1.02
Reflected Deciduous Reflected Deciduous Spectrum 7.0 0.93 -2.0 1.02
Light Source Spectral Graph
(Click to Enlarge)

Spectral Error
SQ-100X
(Original)

Correction Factor
SQ-100X
(Original)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

Reflected Grass Reflected Grass Spectrum 5.0 0.95 -2.2 1.02
RGB LED RGB LED Spectrum -16.4 1.16 -0.8 1.01
Sun Clear Sun Clear Spectrum 0.0 1.00 -2.2 1.02
Sun Cloudy Sun Cloudy Spectrum 0.2 1.00 -1.7 1.02
Under Alfalfa Canopy Under Alfalfa Canopy Spectrum 8.3 0.92 -1.7 1.02
Under Maple Canopy Under Maple Canopy Spectrum 10.1 0.90 -0.9 1.01
Light Source Spectral Graph
(Click to Enlarge)

Spectral Error
SQ-100X
(Original)

Correction Factor
SQ-100X
(Original)

Spectral Error
SQ-500
(Full-spectrum)

Correction Factor
SQ-500
(Full-spectrum)

Under Pine Canopy Under Pine Canopy Spectrum Coming Soon Coming Soon -0.4 1.00
Under Wheat Canopy Under Wheat Canopy Spectrum 8.4 0.92 -1.1 1.01
Valoya RW LED Valoya RW LED Spectrum -29.7 1.30 -6.0 1.06
WWF LED WWF LED Spectrum -7.8 1.08 -1.9 1.02
2 Actinic, 2 Blue Plus 2 Actinic 2 Blue Plus Spectrum 19.9 0.80 -3.0 1.03
3 T5, 1 Actinic 3 T5 1 Actinic Spectrum 10.5 0.90 -2.0 1.02
4 Actinic 4 Actinic Spectrum 16.9 0.83 -10.0 1.11
4 Blue Plus 4 Blue Plus Spectrum 22.9 0.77 -3.0 1.03