Certainly, the larger the sign, the further away your message will be seen. The sooner someone contemplating an illegal behavior (vandalism, graffiti, trespassing) becomes aware of your surveillance system, the more likely you will be to help deter this activity. Savvy property owners actually post several signs - not just at the perimiter of your surveillance camera range, but also in traffic-heavy areas. Multiple signs reinforce your surveillance system and leverage your CCTV investment. The rule-of-thumb for legiblity, is that each 1” of letter height gives 25 feet of viewing distance. Other factors matter, however: lighting, angularity and, if you in a car, speed. The three signs below are most common/ The larger sign (24” tall) might be used along roadways, the 18” tall sign is often used on entrances, sidewalks or pedestrian areas and the smller 10” tall sign is used at the door.