Figure 1. Possible artifact when measuring lateral diffusion of rhodopsin. The two black noisy lines are absorbance traces recorded in configuration a, with a measuring beam jumping alternatively between the two sides of ROS. The arrow indicates the moment at which a half-ROS bleaching flash was applied (hatched area in a). Difference between absorbances at two ROS sides generated by the flash further dissipates, supposedly due to diffusional exchange by rhodopsins. Bold blue line shows the time course of post-flash absorbance changes recorded in configuration b. Here the measuring beam is placed at the ROS center and full-field bleach applied, so no diffusion-related changes was expected. Recordings are made in standard Ringer solution at pH 7.5.