Truzi, nothing bad would happen to restrainer used when film was not fogged other than development would take longer. Restrainer slows down development, especially the lowest densities, but since the lowest densities (fog) would not be there, the negative would develop normally or maybe a tiny bit more contrast than usual. As Michael says: It 'tends' to reduce film speed but, Truzi, only because development takes longer and (only a tiny bit) because the shadow densities are now very slightly suppressed with the restrainer. -David Lyga