Method (10; 20) for the quantitative optical measurement of a characteristic property of at least one analyte in at least one laboratory sample, in particular for the fluorescence measurement of at least one biochemical or biological sample, the method using a laboratory apparatus, which has at least one light source and at least one detector device, the apparatus utilizing at least one sensitivity parameter S, which controls the capability of the laboratory apparatus to detect a signal by means of the at least one detector device, wherein the sensitivity parameter is varied by variation of at least one operational parameter of the detector device, e.g. an electronic gain factor, or wherein the sensitivity parameter is varied by variation of the intensity of source light, which is used to measure the at least one analyte in the at least one sample, the method using the light source for emitting the source light for causing the at least one sample to emit a sample light, and the at least one detector device for detecting sample light and the method utilizing the at least one sensitivity parameter S to detect the corresponding at least one intensity I of the sample light, the method comprising the steps: • determining at least one reference point (S_ref; I_ref); • using at least one first sensitivity parameter S_m1, which is not the same as the parameter S_ref, for measuring at least one first intensity I_m1 of sample light assigned to a first analyte in the sample to obtain at least one measurement point (S_m1; I_m1); • determining a quantity Q1, which is the slope of a line, which is determined by utilizing the at least one reference point (S_ref; I_ref) and the at least one measurement point (S_m1; I_m1), wherein Q1 is calculated according to the formula Q1 = (I_m1 - I_ref) / (S_m1 - S_ref); or according to an interpolation function or a regression function through (S_ref; I_ref) and multiple different measurement points (S_m1; I_m1), • using the quantity Q1 for calculating a first analyte value C_m1, which is proportional to Q1 and which is characteristic for a property of the first analyte, in particular for a concentration CON1 of the first analyte in the at least one sample, wherein CON1 can be calculated according to CON1 = a(C_m1) or CON1 = a (C_m1 - C_m0), wherein a is a predetermined function or a constant, which is in particular determinable using a conventional calibration method, and wherein C_m0 is the value of a blank sample, which does not contain the analyte, wherein the reference point (S_ref; I_ref) is a standardization point (S_fix; I_fix) = (S_ref; I_ref) and the step of determining the standardization point (S_fix; I_fix) comprises the steps: • using the source light and at least one optical standard sample for letting the at least one standard sample emit at least one standard sample light, and letting the detector device detect the at least one standard sample light for determining at least the first intensity I_1 of a first standard sample light as a first function of the variable sensitivity parameter S of the detector device, according to I_1 = c1 ∗ (S - S_1_0) + I_1 0, wherein c1 is a factor depending on the first optical standard sample and S_1_0 and I_1_0 are the parameters for defining the straight line; • utilizing at last one second function I_2; • determining (S_fix; I_fix) to be an intersection point between the at least two functions I_1 and I_2. • determining at least one reference point (S_ref; I_ref); • using at least one first sensitivity parameter S_m1, which is not the same as the parameter S_ref, for measuring at least one first intensity I_m1 of sample light assigned to a first analyte in the sample to obtain at least one measurement point (S_m1; I_m1); • determining a quantity Q1, which is the slope of a line, which is determined by utilizing the at least one reference point (S_ref; I_ref) and the at least one measurement point (S_m1; I_m1), wherein Q1 is calculated according to the formula Q1 = (I_m1 - I_ref) / (S_m1 - S_ref); or according to an interpolation function or a regression function through (S_ref; I_ref) and multiple different measurement points (S_m1; I_m1), • using the quantity Q1 for calculating a first analyte value C_m1, which is proportional to Q1 and which is characteristic for a property of the first analyte, in particular for a concentration CON1 of the first analyte in the at least one sample, wherein CON1 can be calculated according to CON1 = a(C_m1) or CON1 = a (C_m1 - C_m0), wherein a is a predetermined function or a constant, which is in particular determinable using a conventional calibration method, and wherein C_m0 is the value of a blank sample, which does not contain the analyte, • using the source light and at least one optical standard sample for letting the at least one standard sample emit at least one standard sample light, and letting the detector device detect the at least one standard sample light for determining at least the first intensity I_1 of a first standard sample light as a first function of the variable sensitivity parameter S of the detector device, according to I_1 = c1 ∗ (S - S_1_0) + I_1 0, wherein c1 is a factor depending on the first optical standard sample and S_1_0 and I_1_0 are the parameters for defining the straight line; • utilizing at last one second function I_2; • determining (S_fix; I_fix) to be an intersection point between the at least two functions I_1 and I_2.