We compared the properties of rsEGFP with that of the well-known RSFP Dronpa. With the proteins embedded in a 12.5% polyacrylamide layer and using light of 491 nm and 405 nm, a complete on–off cycle took 250 ms for Dronpa and 20 ms for rsEGFP. Dronpa went through <10 cycles before its fluorescence was reduced to 50%, whereas rsEGFP went through ∼1,200 cycles under the same conditions. To compare bleaching, Dronpa and rsEGFP were kept in the on-state by continuous irradiation at 405 nm while fluorescence was generated by irradiation at 491 nm. Whereas Dronpa fluorescence was reduced to 50% within t½ ≈ 30 s, for rsEGFP we measured t½ ≈ 800 s.