SOP 222.08-att-3: GCIC Operations Bulletin #98-07 - Capture and Transmission of Facial Images

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SUBJECT: The Capture and Transmission of Facial Images

CONTACT: Shirley Andrews
Research/Development
404-244-2721 FAX: 404-241-5992

1. This is a highly technical operations bulletin to be used by Georgia Crime
Information Center (GCIC) customers when dealing with vendors providing
mugshot-imaging capability. To ensure compatibility with the Standards and Best
Practices document, agencies should provide this information to any vendor
chosen to provide mugshot-imaging capability.

2. The data format for the Interchange of Facial Images & Scars Marks and Tattoos
(SMT) (titled “Data Format for the Interchange of Fingerprint, Facial, & SMT
Information” (ANSI/NIST-ITL la-1997)) was approved by the American National
Standard Institute (ANSI) on April 7, 1997.

3. The Information Technology Laboratory (ITL), previously the Computer Systems
Laboratory of the National Institute of Standards and Technology (NIST),
sponsored the development of the addendum to the Data format for the
Interchange of Fingerprint Information (ANSI/NIST-CSL 1-1993). This
addendum enhances the original standard by specifying the data elements required
for the exchange of mugshot and SMT information.

4. To effectively exchange Facial Images or mugshots and (SMT) information
across jurisdictional lines or between dissimilar systems, a standard is needed to
specify the content and common format for the data exchange. The data may be
images captured from digital cameras or the digital representation of scanned
photographs or pictures.

5. Listed below are best practices, procedures and equipment specifications for law
enforcement agencies considering the purchase of new systems or the upgrade of
current systems.

a. POSE

The full-face or frontal pose is the most commonly used pose in photo
lineups and shall always be captured. This pose is in addition to profiles
or intermediate angled poses captured to acquire perspective and other
information. For subjects who normally wear eyeglasses, a frontal

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mugshot image should be captured of the subject without glasses. This is
required due to the glare from external illumination. An additional image
can optionally be captured of the subject wearing eyeglasses.

b. DEPTH OF FIELD

The subject’s captured facial images shall always be in focus from the
nose to the ears. Although this may result in the background behind the
subject being out of focus, it is not a problem. For optimum quality of the
captured mugshot, the f-stop of the lens should be set at two f-stops below
the maximum aperture opening when possible.

c. CENTERING

(1) The facial image being captured (full-face pose) shall be in a
position to satisfy all of the following conditions:
(2) The approximate horizontal midpoints of the mouth and of the
bridge of the nose shall lie on an imaginary vertical straight line
positioned at the horizontal center of the image.
(3) An imaginary horizontal line through the center of the subject’s
eyes shall be located at approximately the 55% point of the vertical
distance up from the bottom edge of the captured image.
(4) The width of the subject’s head shall occupy approximately 50%
of the width of the captured image. This width shall be the
horizontal distance between the mid-points of two imaginary
vertical lines. Each imaginary line shall be drawn between the
upper and lower lobes of each ear and shall be positioned where
the external ear connects to the head.

d. LIGHTING

Subject illumination shall be accomplished using a minimum of three-(3)
point balanced illumination. Appropriate diffusion techniques shall also
be employed and lights positioned to minimize shadows, and to eliminate
hot spots on the facial image. These hot spots usually appear on reflective
areas such as cheeks and foreheads. Proper lighting shall contribute to the
uniformity of illumination of the background described in the exposure
requirement.

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e. BACKGROUND

The subject whose image is being captured shall be positioned in front of a
background which is 18% gray with a plain smooth flat surface. A kodak
or other neutral gray card or densitometer shall be used to verify this 18%
gray reflectance requirement. GCIC OPERATIONS BULLETIN 98-07

f. EXPOSURE

The exposure shall be keyed to the background. Several areas of the
recorded 18% gray background shall be used to verify the proper
exposure. The averages of 8-bit Red, Green and Blue (RGB) components
within each area shall be calculated. Each of the RGB means shall fall
between 105 and 125 with a standard deviation of plus or minus 10.
Furthermore, for every area examined, the maximum difference between
the means of any two of the RGB components shall not exceed 10.

g. ASPECT RATIO

The Width:Height aspect ratio of the captured image shall be 1:1.25.

h. MINIMUM NUMBER OF PIXELS

(1) The minimum number of pixels in an electronic digital image shall
be 480 pixels in the horizontal direction by 600 pixels in the
vertical direction. It should be noted that the image quality of the
captured mugshots and facial images will be improved as the
number of pixels in both directions are increased. However, as
images are captured with an increased number of pixels, the 1:1.25
(Width:Height) aspect ratio will be maintained.

(2) Two considerations must be noted regarding this aspect of the
recommendation. First, the normal orientation of many available
cameras is the landscape format that specifies a greater number of
pixels in the horizontal than in the vertical direction. Unless these
cameras capture at least 600 pixels in the vertical direction, it may
be necessary to rotate the camera 90 degrees. Second, the 480x
600 capture format exceeds the VGA display format of 640x480.
Therefore, at a minimum, an SVGA specification of 800x600
pixels will be required to display the facial image. The image will
occupy less than the total number of available horizontal pixels.

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i. COLORSPACE

Captured electronic color facial images are required. Digital images shall
be represented as 24-bit RGB pixels. For every pixel, eight (8) bits will be
used to represent each of the Red, Green, and Blue components. The RGB
colorspace is the basis for other colorspaces including the Y, Cb, Yr and
YUV. Additional color management techniques are available from the
International Color Consortium. Information regarding these techniques
can be downloaded from the following Uniform Resource Locator (URL):

j. PIXEL ASPECT RATIO

Digital cameras and scanners used to capture facial images shall use
square pixels with a pixel aspect ratio of 1:1.

k. COMPRESSION ALGORITHM

The algorithm used to compress mugshot and facial images shall conform
to the JPEG Sequential Baseline mode of operation as described in the
specification approved by the ANSI X3L3 Standards committee. The
target size for a JPEG compressed color mugshot image file shall be
25,000 to 45,000 bytes.

l. FILE FORMAT

The JPEG File Interchange Format (JFIF) shall contain the JPEG
compressed image data. The JFIF file shall the be part of the transaction
file for interchange which conforms to the requirements as contained in
ANSI/NIST-CSL 1-1993 and ANSI/NIST-ITL la1997.

6. APPROVED: __________________________________________ 2-1-02
Paul C. Heppner, Deputy Director for GCIC Date

Retention Schedule: To be retained as part of the SOP until updated.