A couple of reflectance and transmittance spectra from the same sample can be found in the linked publication (calculations based on Fresnel's equations). There are definitely some differences...

Article Employing Theories Far beyond Their Limits-The Case of the (...

Thank you Thomas for your answer. I however cannot see the link to the full paper but i have requested for the full text and will be expecting it. I was actually surprised of this observation while working in the lab as it is a commonly acceptable procedure assuming the logarithmic relationships of reflectance or transmittance for absorption. It makes a lot of sense though that reflectance and transmittance intensities of same sample taken with the same equipment will be different but if their spectra profile also could be different, then there is a serious issue with various absorbance outputs obtained from taking the conventional logarithmic relationships of reflectance or transmittance.

I fully agree with you! Numerous works rely on these logarithmic relationships without taking into account that those relationships usually do not comply with Maxwell's equations. The problem is that it is much easier to employ these relationships than to apply the formalisms appropriate for the optical model that corresponds with the experiment. Accordingly, either the Fresnel equations (semiinfinite medium) or Abeles formalism (finite thickness) must be used, or, in cases where anisotropy plays a role, Berreman's or Yeh's formalism.

Thank you. Can you please send me the full paper you mentioned? I have access only to the abstract and i earlier requested from you the full text. Thank you.