In this work the instrumentation and characterization of a filterradiometer suitable for field measurements of O3 → O(1D) photolysis frequencies, j(O1D), is described. A nonlinear calibration function considering ozone column and solar zenith angle is derived as well as a procedure utilizing an irradiance standard as an absolute reference. The measurement concept is tested by a field comparison with a spectroradiometer. Based solely on laboratory characterizations and simulated solar actinic flux spectra, a systematic deviation of 4% is obtained with a standard deviation of 3% at solar zenith angles below 70¿. The standard deviation rises to 8% at solar zenith angles in the range 70¿--85¿. The systematic difference is within the accuracy of the applied radiometric calibrations while the standard deviation is mainly caused by insufficient synchronization of the different measurement techniques under variable field conditions. In addition, the relative temperature dependence of j(O1D) as a function of solar zenith angle and ozone column is derived which is applicable to any ground-based j(O1D) measurement.