A luminometer (400) includes a light detector (630) configured to sense photons (135). The luminometer (400) includes an analog circuit (915a) configured to provide an analog signal (965) based on the photons (135) emitted from assay reactions over a time period and a counter circuit (915b) configured to provide a photon count (970) based on the photons (135) emitted from the assay reactions over the time period. The luminometer (400) includes a luminometer controller (905) configured to, in response to an analog signal value of the analog signal (965) being greater than a predetermined value, determine and report a measurement value of the photons (135) emitted from the assay reactions over the time period based on the analog signal value of the analog signal (965) and a linear function (1010). Optionally, the linear function (1010) is derived from a relationship between the analog signal (965) and the photon count (970).