CCTV Video Surveillance System Design Questions and Answers

Question 1

A system designer needs to select a camera to provide evidential-quality video to identify a person's face at a distance of 10 meters. According to the DORI standard (IEC EN 62676-4), what is the minimum required pixel density for the 'Identification' level?

Accepted Answer

250 Pixels per Meter (PPM)

Answer

The DORI standard specifies different pixel densities for varying levels of detail. For 'Identification,' which enables the identity of an individual beyond a reasonable doubt, the standard requires a minimum of 250 Pixels per Meter (PPM).

Question 2

A client wants to install a camera pointed towards a building entrance that has a glass door, leading to strong sunlight during the day. This lighting condition causes individuals entering the building to appear as dark silhouettes. Which camera feature is specifically designed to correct this issue by balancing the light for the entire scene?

Accepted Answer

Wide Dynamic Range (WDR)

Answer

Wide Dynamic Range (WDR) technology is designed to handle scenes with a high contrast between bright and dark areas, such as a bright background and a dark foreground. It captures multiple exposures of the scene and combines them to create a single image where details in both the bright and dark areas are visible. BLC brightens the entire image, which can wash out the already bright background, while HLC is for suppressing bright sources like headlights.

Question 3

When specifying a camera for a dimly lit warehouse that operates at night, which camera specification is most critical for determining its ability to produce a clear image in low-light conditions without relying on infrared illuminators?

Accepted Answer

Lux Rating

Answer

The Lux rating of a camera indicates the minimum amount of ambient light required to produce a usable image. A lower lux rating means the camera is more sensitive to light and can perform better in darker environments.

Question 4

You are designing a video surveillance system for a small retail store with 8 cameras, each recording 1080p video (approximately 4 Mbps bitrate) continuously. The client requires a video retention period of 30 days. Which of the following is the closest estimate for the total required storage capacity?

Accepted Answer

10 Terabytes

Answer

To calculate the storage: (4 Mbps per camera * 8 cameras) = 32 Mbps total bitrate. Convert Mbps to GB per day: (32 Mbps / 8 bits/byte * 3600 seconds/hour * 24 hours/day) / 1000^3 bytes/GB ≈ 345.6 GB/day. For 30 days: 345.6 GB/day * 30 days ≈ 10,368 GB, which is approximately 10.4 TB. Therefore, 10 Terabytes is the closest and most appropriate estimate among the choices.

Question 5

A designer is selecting a lens and camera combination to monitor a specific doorway that is 20 meters away. To ensure the doorway fills a significant portion of the camera's view, which two factors are most important to use in a Field of View (FoV) calculation?

Accepted Answer

Lens Focal Length and Sensor Size

Answer

The Field of View (FoV) is determined by the camera's sensor size and the focal length of the lens. A longer focal length will produce a narrower field of view, making distant objects appear larger, while the sensor size defines the overall area that can be captured. These two parameters are essential for calculating the viewing angle and ensuring the target is framed correctly.

CCTV - Closed Circuit Television Practice Test

CCTV - Closed Circuit Television Practice Test

CCTV Video Surveillance System Design Questions and Answers