Both chlorophyll f and chlorophyll d are red-shifted chlorophylls in oxygenic photosynthetic organisms, which extend photon absorbance into the near infrared region. This expands the range of light that can be used to drive photosynthesis. Quantitative determination of chlorophylls is a crucial step in the investigation of chlorophyll-photosynthetic reactions in the field of photobiology and photochemistry. No methods have yet been worked out for the quantitative determination of chlorophyll f. There is also no method available for the precise quantitative determination of chlorophyll d although it was discovered in 1943. In order to obtain the extinction coefficients (ε) of chlorophyll f and chlorophyll d, the concentrations of chlorophylls were determined by Inductive Coupled Plasma Mass Spectrometry according to the fact that each chlorophyll molecule contains one magnesium (Mg) atom. Molar extinction coefficient ε chl f is 71.11 × 10³L mol⁻¹ A₇₀₇ nm cm⁻¹ and ε chl d is 63.68 × 10³L mol⁻¹ A₆₉₇ nm cm⁻¹ in 100% methanol. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.