Choosing a Camera for a Backlit Entrance
A building entrance has a glass door facing south. Daytime sunlight floods the lobby; at night the exterior is dark while the lobby is brightly lit. The customer wants to identify faces of people entering and leaving, plus read vehicle plates in a driveway 15 m away at night. Two cameras are budgeted. The integrator proposes one general-purpose dome covering both the door and the driveway. Frame rate target is 15 fps, and footage must integrate with an existing VMS via ONVIF.
1. Evaluate the single-dome proposal and recommend a better configuration.
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One dome cannot serve both jobs well:
- Face capture at a backlit door needs high dynamic range (WDR) to keep both the bright exterior and the shaded face usable, plus a lens/field of view tight enough that a face spans enough pixels for identification.
- Plate reading at 15 m at night needs a narrow field of view, sufficient resolution at that distance, IR illumination matched to the plate, and a short exposure to freeze motion - requirements that conflict with a wide entrance view and with WDR face capture.
Recommendation: two cameras, each matched to its task. Entrance camera: WDR-capable model aimed to capture faces on approach, positioned to avoid direct sun in the lens, with IR or adequate lighting for night. Driveway camera: longer focal length / higher resolution to give enough pixels per plate at 15 m, with IR illuminator sized for the distance, and exposure settings tuned for plates. Confirm both are ONVIF-compliant with the existing VMS and that the VMS supports the required streams.
2. What do you verify on site before finalizing the entrance camera placement?
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Check the actual pixel density on a face at the expected capture point (measure a test subject at the door and at approach distance), confirm WDR handles the real sun angle at the worst time of day, and check for lens flare/veiling glare from the glass door and sun. At night, verify illumination reaches faces without blowout from the bright lobby behind. For the driveway, measure plate pixel width at 15 m and test read rate at night with real vehicles. Adjust aim, lens, and exposure based on measurements, not assumptions.