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Soils with seasonal or continuous water saturation are characterized by unique redox‐related processes including Fe and Mn oxide reduction. Indicators of reduction in soils (IRIS) devices were created as low‐cost, direct sensors of such reduced chemistry. Such IRIS devices are painted with oxides of Fe or Mn, inserted into the soil, and then removed after a period of time; once removed, the paint lost due to reductive dissolution of these oxides is used to indicate the presence, location, and/or intensity of reducing conditions. However, quantifying the paint removal using existing methods can be subjective and time consuming. Here, we describe the use of the IRIS Imager, an image analysis program that calculates removal of paint from IRIS films inL*a*b* color space (whereL* is lightness,a* is red–green value, andb* is blue–yellow value) by comparing the change in lightness between initial and final IRIS film images. Paint removal from films deployed in flooded rice (Oryza sativaL.) paddy soils were quantified using the IRIS Imager, the grid method, and chemical extractions of IRIS films. All three methods were suitable for quantification of paint removal, but the IRIS Imager provided additional statistics to assess heterogeneity in paint removal on individual films and a less subjective approach to quantifying Mn oxide paint removal when Fe oxidation on Mn films was present. This free software can be used with IRIS devices to reproducibly measure paint removal from Fe oxide and Mn oxide IRIS and Fe oxide precipitation on Mn oxide IRIS.