Abstract: A method and device (10) for making a calibrated measurement of light from an object (E). In a first measurement window (W1), object light (LE) is received from the object (E) onto a beam splitter (11) which splits the light into a signal path (Ps) and a reference path (Pr). A first signal (S1=T·LE·Hs) is measured by a signal detection element (15s) in the signal path (Ps). A second signal (S2=R·LE·Hr) is measured by a reference detection element (15r) in the reference path (Pr). In a second measurement window (W2), calibration light (LC) is received onto the beam splitter (11). A third signal (S3=R·LC·Hs) is measured by the signal detection element (15s) in the signal path (Ps). A fourth signal (S4=T·LC·Hr) is measured by the reference detection element (15r) in the reference path (Pr). A measurement value of the object light (LE) is determined based on the measured signals (S1,S2,S3,S4).