The three form factors differ in mounting method, aiming flexibility and working distance. Match the scene to the type.

• Dome: ceiling-mounted, tidy in appearance and hard to read for direction. Ideal for indoor corridors, lift lobbies, offices and retail. The trade-off is limited re-aiming after installation and a generally shorter working distance.
• Bullet: directional, well cooled, and able to carry long lenses and larger sensors. Suited to outdoor perimeters, roads and car parks at medium to long range, and easier to supplement with sunshields and illuminators.
• PTZ: 360-degree rotation and optical zoom let one unit cover a large area. Right for plazas, industrial estates and entrances with complex vehicle and pedestrian movement needing active tracking. Cost and maintenance complexity are correspondingly higher.

A good combination: bullets for fixed perimeter coverage, PTZs for flexible gap-filling at plazas and gates, domes indoors for appearance. Where types are mixed in one area, standardise time sync and stream policy to make later review straightforward.