Event-related potential (ERP) studies revealed an early posterior negativity (EPN) for emotionally arousing pictures. Two studies explored how this effect relates to perceptual stimulus characteristics and stimulus identification. Adding various amounts of visual noise varied stimulus perceptibility of high and low arousing picture contents, which were presented as rapid and continuous stream. Measuring dense sensor event-related potentials, study I determined that noise level was linearly related to the P1 peak. Subsequently, enlarged EPNs to emotionally arousing contents were observed, however, only for pictures containing low amounts of noise, which also enabled stimulus identification as shown by study II. These data support the notion that the EPN may serve as a measure of affective stimulus evaluation at an early transitory processing period.