A method of determining a measurement value on the basis of a plurality of single molecule events of marker molecules in a sample comprises the steps of selecting the marker molecules from a group of marker molecules which are transferable between a measurable state in which a measurement signal necessary for determining the at least one measurement value is obtainable from the marker molecules and a non-measurable state, of providing the marker molecules in the sample at such an absolute concentration that the at least one measurement value is not determinable, if all marker molecules are in their measurable state, and adjusting a measurement concentration of the marker molecules in the measurable state by means of applying the physical signal to the sample at such an intensity that the at least one measurement value is determinable within a defined measurement area of the sample.