Photosynthesis-irradiance (PI) experiments that measure the uptake of <sup>14</sup>C labelled bicarbonate over a light gradient established in an incubator are foundational to computations of primary productivity and models of photosynthesis in ecosystem models. We present a compilation of PI data collected over the last 50 years with largely consistent methods, totalling 3751 PI curves from the North Atlantic (2384 curves), Arctic (1209), North Pacific (90) and Indian (68) oceans. Unlike many compilations, we present original measurements of photosynthetic rate and irradiance, together with derived photosynthesis-irradiance (PI) model parameters as well as detailed metadata including experimental design, environmental conditions, and methodological variation. Using this database and a suite of PI models, we show how parameter estimates typically vary across observations and model formulations, and demonstrate how differences in experimental design and methodology can systematically affect parameter values. We show that quality statistical conversion of parameter values from one model to another is often possible, although direct estimation of parameters from original data is always preferable.