As the soil in southern Sweden recovers from acidification during the 20th Century, iron (Fe) and dissolved organic carbon (DOC) increasingly enter freshwater systems, resulting in "brownification." This process, characterised by light absorption and scattering of waterborne particles and dissolved molecules, causes a brown-yellow colouration that disrupts freshwater ecosystems. Although extensive research has shown that DOC and Fe strongly associate and transport together, their combined effect on light absorption remains poorly understood. This study assessed water quality from Lake Bolmen to investigate how DOC influences Fe light-absorbing properties. Using the data obtained from field samples, a laboratory study was designed and conducted where known concentrations of DOC and Fe were mixed in artificial river water and analysed using UV-Vis spectroscopy. The results revealed that Fe light absorption is markedly enhanced at very low C ratios, beyond which the impact of this enhancement on overall brownification is minimal. These findings provide new insights into the light-absorbing behaviours of Fe and DOC and suggest priorities for future brownification mitigation strategies.