# Algorithms Used for Microspectroscopy

> Transmittance calculates a transmission spectrum from a sample and reference single-beam spectra.

Source: https://www.microspectra.com/support/the-science/algorithms-used-for-microspectroscopy/

![Light is transmitted through the sample, collected by the objective and focused onto the aperture and simulaneously an image and spectrum are collected.](https://www.microspectra.com/wp-content/uploads/2026/08/msp_optical_path-web.jpg)

![Transmission spectrum from a microspectrophotometer.](https://www.microspectra.com/wp-content/uploads/2026/08/fpd_pixel_spectrum.jpg)

## Transmittance

Transmittance calculates a transmission spectrum from a sample and reference single-beam spectra.

*From Two Single-Beam Spectra* a transmission spectrum using the following formula:

![Percent transmission calculation](https://www.microspectra.com/wp-content/uploads/2026/08/formula_per_trans_calc.jpg)

where R is the single beam spectrum of the reference material, S is the single beam spectrum of the sample and D is the dark counts of the system.

*From Absorbance Data* a transmission spectrum can be generated using the following formula:

![Convert absorbance to percent transmission.](https://www.microspectra.com/wp-content/uploads/2026/08/formula_conv_abso.jpg)

where A is the absorbance value. This is a calculation from data that has already been collected.

## Absorbance

Absorbance calculates an absorption spectrum from a sample and reference single-beam spectra or from a transmission spectrum.

*From Two Single-Beam Spectra* an absorption spectrum can be generated using the following formula:

![Absorbance calculation](https://www.microspectra.com/wp-content/uploads/2026/08/formula_ab_calc.jpg)

where R is the single beam spectrum of the reference material, S is the single beam spectrum of the sample and D is the dark counts of the system.

*From Transmission Data* an absorption spectrum can be generated using the following formula:

![Convert percent transmission to absorance.](https://www.microspectra.com/wp-content/uploads/2026/08/formula_conv_perc.jpg)

where %T is the percent transmittance value. This is a calculation from data that has already been collected.

## Reflectance

Reflectance calculates a reflectance spectrum from a sample and reference single-beam spectra or from an log 1/R spectrum.

*From Two Single-Beam Spectra* a reflectance spectrum can be generated using the following formula:

![Percent reflectance calculation.](https://www.microspectra.com/wp-content/uploads/2026/08/formula_perc_ref_calc.jpg)

where R is the single beam spectrum of the reference material, S is the single beam spectrum of the sample and D is the dark counts of the system.

A microspectrophotometer such as the [2030PV PRO™](https://www.microspectra.com/products/2030-microspectrophotometer/) measures all three: transmittance, absorbance and reflectance.