Histogram of the angular Einstein radius θ_E relative to the angular size of the source stars θ_S. Histograms are shown for ground-based I-band, ground-based K-band, and space-based H-band observations from top to bottom. Red, blue, and green histograms in each plot correspond to Jupiter-, Neptune-, and Earth-mass FFPs, respectively. The vertical line shows where θ_E = θ_S, indicating where finite source effects become dominant. The dashed histogram in each lens mass shows the distribution if a point source is assumed for all events, and the solid histograms are the distributions when the finite source effect is included.