7. Cameras
Cameras used in CCTV systems should adhere to the following recommendations:
7.1. Black-and-White Versus Color Cameras
Although black-and-white video cameras may provide better image
resolution than color cameras, the information available in color
images may provide important investigative information. Therefore,
the choice of cameras is left to the commercial institution, dependent
on the intended use of the recorded images.
7.2. Camera Detector Size
Video and digital cameras use detectors that come in a variety
of sizes. Typical sizes are 1/4, 1/3, and 1/2 inches. The size
of the detector will have a direct impact on the focal length
of the camera lens. See Section 7.5 for further information.
7.3. Camera Resolution
In order to meet the Scientific Working Group on Imaging Technology
guidelines, analog video cameras must have an output resolution
of at least 400 horizontal lines. Digital video cameras must have
an output resolution of at least 480 horizontal lines. Cameras
that have higher resolutions are strongly recommended.
7.4. Camera Infrared Characteristics
The detectors used in black-and-white video cameras may be sensitive
to a part of the infrared spectrum that is outside of the normal
range of human visual perception. This can improve the ability
of the camera to record in low-light situations.
Due to the fact that images acquired by infrared-sensitive cameras
can make some dark clothing and other objects appear to be lighter
than they actually are, it is recommended that infrared-sensitive
cameras not be used to record scenes that are well-illuminated.
Many cameras are equipped with filters that can mitigate this
effect. This does not apply to most color cameras that normally
contain an infrared barrier filter to block infrared light.
The use of infrared-sensitive cameras should be noted in the system
documentation (see Section 9.1).
7.5. Lens, Focal Length, and Field-of-View
The selection of lenses will be dictated by the field-of-view
to be covered by each camera, as well as by the size of the camera's
detector.
For cameras placed to record images at a point-of-customer transactions,
such as a teller window (See Section 5.3), the area of interest
(e.g., face, license plate) should cover approximately 15 percent
or more of the camera's field-of-view (based on the recommended
minimum resolution found in Section 7.3). For an average human
head that is six-inches wide, a three-foot-wide field-of-view
will meet this guideline. For a license plate width of approximately
12 inches, a six-foot-wide field-of-view is sufficient.
The focal length necessary to achieve an approximately three-foot-wide
field-of-view for a given detector size and camera-to-subject
distance is provided in Table 3. The camera must be in focus at
the position of this subject.
Table 3. Approximate Focal Length (in
mm) Needed for Three-Foot-Wide Field-of-View
 |
Distance to
subject (in feet
|
2 |
5 |
10 |
15 |
20 |
30 |
Detector size
(inches) |
1/4" |
2.3 |
5.9 |
11.7 |
17.6 |
23.5 |
35.2 |
| 1/3" |
3.1 |
7.8 |
15.7 |
23.5 |
31.3 |
47.0 |
| 1/2" |
4.0 |
10.1 |
20.2 |
30.3 |
40.4 |
60.7 |
| (Differences in the
units used to describe these resolution recommendations are
due to the differences in the industry standards used to describe these media.)
|
Cameras that provide overviews of interior and exterior
locations should have their focal lengths selected so as to meet
the field-of-view requirements of the facility. However, exit cameras
should have sufficient depth-of-field to be in focus at distances
of three feet and beyond to ensure that subjects exiting the facility
will be in focus.
7.6. Exposure Control
Cameras should be equipped with automatic mechanisms to ensure
proper exposure under varying lighting conditions. Such mechanisms
include, but are not limited to, automatic gain circuitry, day/night
sensor switching, and lenses with automatic iris functions.
7.7. Camera Housings
Cameras may require coverings and environmental controls to protect
them from the elements or tampering. Clear coverings placed in
front of camera lenses will reduce image quality; therefore, unless
there are specific environmental or security concerns that require
camera housings, it is recommended that they not be used.
8. Media
Media, including analog videotapes, compact discs, digital video tapes,
and digital versatile disks, should be of high quality and meet equipment
manufacturers' specifications. Low-quality media can result in
damaged equipment and poor images.
9. System Maintenance
CCTV systems should be maintained in a manner that ensures their
proper function over their entire lifetime. Therefore, the following
recommendations should be adhered to:
9.1. System Documentation
Institutions should maintain documentation regarding their CCTV
systems that includes the following information:
- Make and model of all system components, including recorders,
cameras, lenses, and multiplexer/switcher. For digital systems,
this information should include software and hardware information,
including software version. If infrared-sensitive cameras are
in use, their location should be documented. An example of a
system information sheet is included in Appendix C. If possible,
a photocopy of the maintenance record should be included.
- Adequate system documentation should be included at the site.
This includes instructions for downloading and outputting recordings.
- Point-of-contact information for system installer and/or
system maintenance organization, to include at least two names
and telephone numbers.
- Site plan showing all equipment placement (including recorders),
as well as field-of-view for each camera. Appendix C includes
an example of a site plan.
This information should be verified monthly and made available
to responding law enforcement officials on their arrival at the
scene.
9.2. System Validation and Maintenance
Prior to use, systems must be validated to meet the requirements
of Section 4. The systems must be capable of acquiring, recording,
and producing output images that are of sufficient quality to
enable law enforcement officials to identify the people and objects
depicted therein. Revalidation of these requirements must occur
every time the system is altered.
A variety of system checks and maintenance are necessary at different
times. If system errors are found, steps to correct them should
be implemented.
A maintenance log must be maintained to document all system-validation
activities, checks, and maintenance activities.
Table 4 provides a calendar for these checks and maintenance items
that should be recorded on a maintenance log.
Follow
this link to Table 4.
9.3. Maintenance of Recording Media
Institutional requirements will dictate the length of time for
which recorded images must be archived.
All recording media has an expected usable life span. Based on
that life span, policies should be developed to ensure that media
is replaced before this period expires. For example, it is recommended
that VHS video tapes be reused no more than 12 times and that
they be replaced on an annual basis. This use of extended time-lapse
mode may drastically shorten the life span.
For digital recording devices, manufacturer's recommendations
for maintenance and the device service-life replacement schedule
should be observed. A regular ongoing (automated) inspection of
hard drives should be conducted to ensure that the disk(s) is/are
functioning properly and that there are no bad sectors or other
hardware errors that could result in a loss of data. Other reusable
media must be recertified no less frequently than the manufacturer's
guarantee period.
Institutions should establish policies regarding the marking of
removable media so that the most recent date of recording will
be documented.
10. Retention of Recordings
It is recommended that analog videotapes be retained for a minimum
of 31 days before being reused. This coincides with the 12-time
use recommendation. For ease of retrieval, each videotape should
be sequentially numbered, and the dates and times recorded on each
tape should be written on a label on the videotape.
Due to the nature of digital recordings, the Scientific Working
Group on Imaging Technology recommends that recordings be retained
for the longest time possible (minimum of 10 days) with the least
amount of compression available in the system's capabilities.
Storage capacity to meet these needs must be
considered.
11. Evidence-Handling Procedures
This section addresses procedures to follow when law enforcement
response is necessary. This may be in response to a robbery, or
it may be related to other criminal investigation.
11.1. Documentation for Law Enforcement
The system documentation, as described in Section 9.1, including
equipment information, site plan, contact information, and maintenance
log, should be made available to responding law enforcement officials.
Any additional pertinent information regarding the recording or
the incident itself should be noted, such as incident time, record
mode, and discrepancies between actual time and recorder time.
Appendix C includes an example of documentation.
11.2. Handling Evidentiary Recordings
Following an incident involving immediate law enforcement response,
it is necessary to ensure that the recorded images are secured.
Unless the possibility exists that the images may be overrecorded
or overwritten, the recording should not be stopped until law
enforcement officials arrive.
11.2.1. Video-cassette tape systems
Upon terminating a recording, the tape should be removed from
the recording device and the recording tab immediately removed
or shifted to the record-disabled setting. The tape should not
be played again prior to the arrival of law enforcement officials.
The name of the institution and identity of the person performing
this function should be marked on the exterior of the cassette
housing, along with the time and date of removal.
Prior to transfer to law enforcement officials, steps must be
taken to ensure that the tape is not mishandled or damaged.
This includes keeping the tape away from magnetic fields, such
as those generated by televisions, radios, and speakers. The
tape should be maintained at room temperature and out of direct
sunlight. Tapes should not be stored in vehicles for an extended
period of time.
Personnel qualified to assist law enforcement in recovering
images from the tape should be identified and made available
prior to the arrival of law enforcement officials.
11.2.2. Digital video systems
The following steps should be followed:
- Upon terminating a recording, personnel qualified to assist
law enforcement in recovering images from the CCTV system
should be identified and made available (in person or by telephone)
to offer technical assistance.
- Law enforcement officials will coordinate with appropriate
personnel to view and retrieve the best image(s) prior to
the officials' departure from the crime scene. When immediate
transmission of images is necessary to expedite distribution
from the crime scene, the images should be transmitted by
network, e-mail, compact disc, or other available means. Images
shall be provided to law enforcement in the TIFF, BMP, or
JFIF (JPG) formats. If the facility uses a remote location
for the storage of recorded images, then the facility will
provide the images to an address designated by the law enforcement
officials.
- The facility's security personnel will produce at least
two copies of the relevant images and video on compact disc
(CD) or digital versatile disk (DVD) (nonrewritable) in the
nonproprietary formats as well as the original native format.
- In the event of alarm-trigger incidents as described in
Section 6.8, law enforcement would like all video and relevant
data that were recorded five minutes before the alarm-trigger,
the entire incident, and five minutes after the incident.
This is barring any outside circumstances when it is required
to save a longer period of time (e.g., casing of the bank).
- If additional retrieval of video recording is warranted,
law enforcement officials will notify the facility's security
personnel to secure the hard drive or retrieve additional
video and data. The facility will be required to maintain
all recorded video and data on a rolling ten-day period from
the event of a crime. This means that at the date of the crime,
law enforcement officials would be able to review all video
for ten days prior to the crime. As an example, two days after
the crime, law enforcement officials would be able to review
all video for eight days prior to the crime and so on.
- When the relevant video, images, and data have been copied,
each shall be labeled with the name of the institution and
identity of the person performing this function, along with
the time and date of removal. This information should not
be written directly on the media but preferably on a label
that is affixed to a protective container, such as a jewel
case, sleeve, or clamshell enclosure.
Appendix A: References
Aldridge, J. CCTV Operational Requirements Manual Version 3.0.
Police Scientific Development Branch, United Kingdom Home Office,
Publication Number 17/94, 1994. Available:
http://www.crimereduction.gov.uk/cctvminisite22.htm.
Aldridge, J. and Gilbert, C. Performance Testing CCTV Perimeter
Surveillance Systems. Police Scientific Development Branch,
United Kingdom Home Office, Publication Number 14/95, 1995.
Atkinson, D. J., Pietrasiewicz, V. J., and Junker, K. E. Video
surveillance equipment selection and application guide, National
Institute of Justice Guide 201-99. In: Law Enforcement and Corrections
Standards and Testing Program, February 2000. Available:
http://www.ojp.usdoj.gov/nij/pubs-sum/179545.htm.
Brown, B. Crime Reduction: Closed Circuit Television in Town
Centres: Three Case Studies. United Kingdom Home Office
Police Research Group. Crime Detection and Prevention Series. Publication
Number 68, 1995. Available: http://www.crimereduction.gov.uk/cctv1.htm.
Diffley, C. and Wallace, E. CCTV: Making it Work. Training Practices
for CCTV Operators. Police Scientific Development Branch, United
Kingdom Home Office, Publication Number 9/98, 1998. Available:
http://www.homeoffice.gov.uk/docs/cctv9_98.pdf.
Green, M. W. Appropriate and effective use of security technologies
in U.S. schools. In: A Guide for Practical School Security Applications.
September 1999. Available:
http://www.ncjrs.org/school/home.html.
Griffiths, A. CCTV: Making It Work. Time and Date Displays.
Police Scientific Development Branch, United Kingdom Home Office,
Publication Number 13/98, 1998.
Mather, P. Guidelines for the Handling of Video Tape. Police
Scientific Development Branch, United Kingdom Home Office, Publication
Number 21/98, 1998.
Nichols, L. J. Use of CCTV/Video Cameras in Law Enforcement.
International Association of Chiefs of Police. March 2001. Available:
http://www.theiacp.org/documents/pdfs/Publications/UseofCCTV.pdf.
Police Scientific Development Branch. Digital Imaging Procedure
Version 1.0. Police Scientific Development Branch, United Kingdom
Home Office, Publication Number 02/2002, 2002. Available:
http://www.homeoffice.gov.uk/docs/digimpro.pdf.
Rason, J., Kent, T., Sall, I., Gugenheim, P., and Walker, S. Assessment
of the ADVIS, IMPRESS, VIEW Video Enhancement System for the
UK Police Service. Police Scientific Development Branch, United
Kingdom Home Office, Publication Number 1/2000, 2000.
Scarman Centre National CCTV Evaluation Team, National Evaluation
of CCTV: Early Findings on Scheme Implementation: Effective Practical
Guide. United Kingdom Home Office Statistical Bulletin 5/03,
2003. Available:
http://www.crimereduction.gov.uk/cctv32.htm.
Security Industry Association, 1998-1999 CCTV for Public Safety
Report, Security Industry Association, 1998. Available:
http://www.siaonline.org/response.asp?c=storeproduct_59&r=1024.
Tilley, N. Crime Reduction: Understanding Public Car Parks, Crime
and CCTV: Evaluation Lessons from Safer Cities, United Kingdom
Home Office Police Research Group. Crime Prevention Unit Series
Publication Number 42, 1993. Available: http://www.crimereduction.gov.uk/cctv2.htm.
Wallace, E. and Diffley, C. CCTV: Making it Work: Guidance on
Recruitment and Selection Practice for CCTV. Police Scientific
Development Branch, United Kingdom Home Office, Publication Number
8/98, 1998.
Wallace, E. and Diffley, C. CCTV: Making it Work: CCTV Control
Room Ergonomics. Police Scientific Development Branch, United
Kingdom Home Office, Publication Number 14/98, 1998.
Appendix B: Technical Guidelines for Lighting
In this document, illuminance is measured in Lux. Some older documents
and references may refer to the measurement in foot candles (one-foot
candle is approximately equal to 11Lux).
To provide good-quality camera images, a minimum of 277 to 333Lux
of illumination should be provided in the customer areas, office areas,
hallways, stairways, and exits where there is camera coverage.
Exterior self-service facilities, such as automated teller machine
vestibules or drive-up lanes, should have a minimum of 110Lux of illumination
24-hours daily to ensure good image quality.
Exterior areas, such as sidewalks, entrances, night depository areas,
that have camera coverage should have a minimum of 55Lux of illumination.
Parking lots with camera coverage should have a minimum of 11Lux of
illumination at ground level.
Supplementary surface lighting may be necessary for adequate illumination
for the face of anyone using an automated teller machine or other
self-service resource.
Appendix C: System Documentation and Site
Plan Examples
| System Equipment Information |
|
| Recorder make and model________________________________________________________ |
| Multiplexer make and model_______________________________________________________ |
| Camera/s make and model _______________________________________________________ |
| Are any cameras infrared-sensitive and if so identify_________________________________ |
|
Video format (circle) VHS SVHS DVR PC
Other______________________________________________________________________ |
If DVR or PC-based:
Hardware manufacturer_____________________________________________________ |
| Software name and version___________________________________________ |
Is a copy of the most current maintenance/service log attached?
(circle) YES NO |
| Does the system record multiple cameras? (circle) YES NO |
| If yes, how many?___________________________________________________ |
|
|
|
|
|
|
|
|
Contact Information
|
|
| Recording system point of contact _______________________________________ |
| Telephone: ____________________________________________________________ |
| Institution point of contact ______________________________________________ |
| Telephone: ___________________________________________________________ |
|
|
|
|
If the system records multiple cameras, note the camera location
and angle view. Use the following diagrams as examples.
|
| |
|
Include the following additional information in the event
of a law enforcement response:
|
What record mode was the system? (circle) 2 hour, 6 hour,
12 hour,
24 hour, 48 hour, 72 hour, |
| Other_________________Unknown_________________ |
Does the recorded date/time accurately represent the time
of day?
(circle) YES NO |
| Date and time of incident |
| _____________________________________________________________________________ |
| Date and time of incident on tape______________________________________________ |
| Date and time recording removed from equipment |
| ______________________________________________________________________________ |
|
| Other Information: |
| ______________________________________________________________________________ |
| ______________________________________________________________________________ |
|
