Table 1.

ONE vs TWO. Single molecule fluorescence methods based on one dye and two dyes are compared. They are complementary to each other regarding the precision or range of distance required for the measurement.

	ONE	TWO
Distance precision	> 1.5 nm	< 0.5 nm
Photon budget	10,000 photons	100 photons
Range of distance	unlimited	2 ~ 8 nm
Frame of reference	absolute position (two or three dimensional)	relative distance or orientation (one dimensional)
Requirement for low drift and low vibration equipment	very high	low