I don't know how do they calculate it but they specify it on the product page: https://www.ophiropt.com/infrared/ https://www.ophiropt.com/infrared/ Ranges of

I don't know how do they calculate it but they specify it on the product page: https://www.ophiropt.com/infrared/ https://www.ophiropt.com/infrared/ Ranges of identification, recognition and detection.