Is there a scientific way to measure reflection coefficients on site?

I once heard you can use a lux meter for measuring the reflectance of materials. Is this scientific and reliable at all?

The method was using a lux meter perpendicular to the surface, once inward and once outward. Then you can calculate the reflectance by having these numbers. I am skeptical about this method but I would like to know if someone has scientific backgrounds for this or any other method that works.

Thank you in advance.

the method your are referring to, is a common way to measure reflectivity values, you can find out about the accuracy of this method and 4 other methods in this study:

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@Nimafo Thank you very very much for your help.

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@Nimafo just a quick question; how about [

ASTM E1331 - 15(2019)


Although the paper that you provided shows both HDR and Database-based results match this practice.

I read the descriptions of the document, it seems to be an accurate method, but it requires colorimeter and spectrophotometer which I don’t think this would be a common way of measuring,
at least I haven’t seen any one using this method for daylighting studies.
maybe someone else can help you more with that.