This paper presents a detailed analysis of the capabilities of imaging luminance measuring devices for determining discomfort glare. Common opinions on light-emitting diode (LED)-based street lighting luminaires say these products cause high glare. This paper contains the results of calculations and thoughts on the potential measurement errors arising from the incompatibility of the measuring device parameters (number of pixels, sensor dimensions and focal length) to the resolution of the human eye. There are also some cases presented where this incompatibility is of the highest importance, i.e., for the luminance distribution measurements connected with identifying a discomfort glare problem caused, in particular, by multi-source LED luminaires.