ISO/IEC 19794-5:2005/Amd 1:2007

INTERNATIONAL ISO/IEC
STANDARD 19794-5
First edition
2005-06-15
AMENDMENT 1
2007-12-15
Information technology — Biometric data
interchange formats —
Part 5:
Face image data
AMENDMENT 1: Conditions for taking
photographs for face image data
Technologies de l'information — Formats d'échange de données
biométriques —
Partie 5: Données d'image de la face
AMENDEMENT 1: Conditions de prise de vues pour données d'image
de la face
Reference number
ISO/IEC 19794-5:2005/Amd.1:2007(E)
©
ISO/IEC 2007
ISO/IEC 19794-5:2005/Amd.1:2007(E)
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ii © ISO/IEC 2007 – All rights reserved

ISO/IEC 19794-5:2005/Amd.1:2007(E)
Contents Page
Foreword. iv
Introduction . v
B.1 Scope .1
B.2 Photography recommendations.2
B.2.1 Recommendations for a photo studio or store .2
B.2.2 Recommendations for photo booths.6
B.2.3 Recommendations for a registration office environment .9
B.3 Guidelines for printing .10
B.3.1 Spatial and tonal resolution trade-offs.11
B.3.2 Recommended printing quality.11
B.3.3 Use of a photo template .12
B.4 Guidelines for scanning.12
B.4.1 Sampling frequency and quantization levels.13
B.4.2 Spatial resolution.13
B.4.3 Output colour space.13
B.4.4 Saturation .13
B.4.5 Image compression .13
B.5 Face image quality assessment software .13
B.6 Tables of the recommendations.15
B.6.1 Scene setting.15
B.6.2 Photographing .17
B.6.3 After photographing .18
B.6.4 Photographic quality .19
B.7 Experimental data.19
B.7.1 Experimental results of face recognition in a photo studio and photo booth .19
B.8 Photographic examples .20
B.8.1 Photographic examples at a photo studio .21
B.8.2 Photographic examples at a photo booth.26

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ISO/IEC 19794-5:2005/Amd.1:2007(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
Amendment 1 to ISO/IEC 19794-5:2005 was prepared by Joint Technical Committee ISO/IEC JTC 1,
Information technology, Subcommittee SC 37, Biometrics.

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ISO/IEC 19794-5:2005/Amd.1:2007(E)
Introduction
This part of ISO/IEC 19794 is intended to provide a Face Image Format for face recognition applications
requiring the exchange of face image data. Its typical applications include:
a) Human examination of high resolution facial images;
b) Human verification of identity;
c) Computer automated face identification;
d) Computer automated face verification.
To enable applications on a wide variety of devices, including devices that have limited data storage, and to
improve face recognition accuracy, ISO/IEC 19794-5 specifies not only a data format, but also scene
constraints (lighting, pose, expression, etc.), photographic properties (positioning, camera focus, etc.), and
digital image attributes (image resolution, image size, etc.).
This part of ISO/IEC 19794 includes an informative annex, Annex A, entitled “Best practices for Face Images”.
Although Annex A provides guidance on topics such as subject pose and expression, image compression
ratio, color, geometric distortion, spatial resolution and head size, it does not guide photographers or the
designers and operators of photo booths concerning how, for example, they might arrange lighting and
reflective surfaces relative to the camera and subject. It also doesn’t provide specific advice on the acceptable
amount of variation in illumination across the face, on how to avoid shadows on the face or background, or on
a user interface that would ensure proper head positioning.
This Amendment is Annex B to ISO/IEC 19794-5 and is entitled “Conditions for taking photographs for face
image data”. It provides expert guidance for the design of photographic studios, photo booths and registration
offices and, as such, it supplements the information provided in this Part of ISO/IEC 19794. It also provides
guidance on printing quality and on scanning printed face photographs.

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ISO/IEC 19794-5:2005/Amd.1:2007(E)

Information technology — Biometric data interchange
formats —
Part 5:
Face image data
AMENDMENT 1: Conditions for taking photographs for face image
data
Page 46
Add the following Annex after Annex A.

Annex B
(informative)
Conditions for taking photographs for face image data
B.1 Scope
The purpose of this annex is to provide expert guidance (i.e., best practices) for the photography of faces,
especially when the resulting images are to be used for purposes of identification, either by automated face
recognition systems or by human viewers. This guidance is intended for owners and operators of photography
studios, photo stores and other organizations producing or requiring either conventional printed photographs
or digital images of faces that may be used in applications for passports, visas, or other identification
documents and when those images are required to conform to the frontal image types of this part of
ISO/IEC 19794. This guidance is also intended for the designers and operators of photo booths, if those
booths are required to provide face images conforming to the specifications of this standard. This annex may
also be appropriate source material to application developers, application profile standard developers, or
others making more general use of this standard.
There are many factors that affect face recognition system performance, including the individual’s
appearance, such as his or her facial characteristics, hair style, and accessories, and the acquisition
conditions, such as the camera’s field-of-view, focus, depth-of-field, background, and lighting. The acquisition
conditions have, potentially, a greater influence on face recognition accuracy than the individual’s appearance
and, of course, are controllable by the preparer of the face images.
This annex provides recommendations for acquiring two-dimensional (2D) face images directly with an
analogue, digital, or video camera, as well as for image data acquired through traditional photo printing and
digital scanning. [The acquisition of three-dimensional (3D) images is out of the scope of this annex.]
This annex may also be appropriate source material for application developers, application profile standard
developers, or others making more general use of this standard.
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ISO/IEC 19794-5:2005/Amd.1:2007(E)
B.2 Photography recommendations
This clause provides recommendations for photographing (acquiring) face images in a portrait studio, photo
store, photo booth, registration office, or other facility. Guidance concerning the positioning of the subject and
camera is provided, as well as several examples of alternative lighting arrangements. The intent of this
guidance is to ensure that the subject’s face is properly positioned and uniformly illuminated, thereby
producing images that are compliant with this International Standard and are without shadows or hot spots on
the face or excessive glare in eyeglasses.
B.2.1 Recommendations for a photo studio or store
A photo studio or a photo store is typically a professionally operated facility, equipped with an analogue or
digital camera, multiple adjustable light sources, a suitable background or backdrop cloth, and subject
positioning apparatus designed to obtain high quality portraits. This section provides expert guidance for the
owners and operators of such facilities when they must produce photographs compliant with the requirements
of this standard.
B.2.1.1 Recommended positioning and distance between camera and subject
The following recommendations concern the positioning of the subject and the camera.
⎯ The camera-to-subject distance should be within the range of 1.2 to 2.5 m. Arranging the lighting without
creating shadows will likely be difficult if the camera is placed any closer to the subject.
⎯ Proper focus and depth-of-field will be assured by pre-focusing the lens at the distance of the subject’s
eyes and by selecting an appropriate aperture (F-stop) to ensure a depth-of-field of at least 10
centimetres, or approximately the distance from a subject’s nose to ears. The depth-of-field of a lens is
dependent upon its focal length, its effective aperture, and the focus distance. Point sources which are
closer or farther than the distance at which a lens is well focused will be blurred, with the extent of the blur
described by a “circle of confusion.” If the maximum diameter of the circle of confusion is limited by, for
example, the spacing between adjacent pixels in a CCD image sensor, the front and rear distances from
the plane of optimum focus that produce acceptably focused images can be determined. The sum of
these front and rear distances is the depth-of-field (D ).
DoF
D = D + D
DoF front rear
cFs(s− f )
D =
front
f + cF(s− f )
cFs(s− f )
D =
rear
f − cF(s− f )
where :
D = the front focal distance, the distance from the plane of focus
front
to the plane closest to the lens that is still in acceptable focus,
D = the rear focal distance, the distance from the plane of
rear
focus to the plane farthest from the lens that is still in acceptable focus,
c = the diameter of the circle of confusion,
s= the distance from the lens to the object plane (subject's face), and
F= f/a is the F - stop, the lens focal length f divided by the effective lens
aperture a
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Figure B.1 illustrates these dimensions.
s
Object
Image
Plane
Plane
Lens
c
D D
rear front
a
D
DoF
Figure B.1 — Dimensions for depth-of-field calculations
• The optimum height of the camera is at the subject’s eye-level. Height adjustment can be done by
either using a height-adjustable stool or adjusting the tripod’s height.
• The subject should be instructed to look directly at the camera and to keep his or her head erect and
shoulders square to the camera. The rotation of the head should conform to the requirements of 7.2.2.
less than +/- 5º
Camera
1.2 - 2.5m
Side view
Figure B.2 — Preferred distance and alignment of camera and subject
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ISO/IEC 19794-5:2005/Amd.1:2007(E)
B.2.1.2 Example of exposure metering at various spots on a subject
The figure below illustrates exposure value (EV) measurement at four spots on a subject’s face, namely the
left and right cheeks, forehead, and chin. The measurements may be made by placing an incident light meter
at the position of a subject’s face and pointing the meter towards the camera. The four readings should be
within 1 EV of one another. If they are not within 1 EV, the lights should be repositioned more symmetrically
about the subject-to-camera line.

Figure B.3 — Positions of incident light meter for exposure value measurement
EV is the value given to any combination of shutter speed and aperture (F-stop) that results in the same
exposure. By definition, an EV value of 0 corresponds to a shutter speed of 1 second and an aperture of F1.0,
for a film speed or equivalent image sensor sensitivity of ISO 100. EV is defined by the following equation:
⎛ ⎞
F
⎜ ⎟
EV= Log = 2Log (F)− Log (T) ,
2 2 2
⎜ ⎟
T
⎝ ⎠
where F is the F-stop setting and T is the exposure time. A change of 1 EV corresponds to a one F-stop
aperture increase or decrease or a halving or doubling of the exposure time.
B.2.1.3 Example configurations for a photo studio or store
Described below are three examples of lighting and subject and camera positioning that are applicable to
photographic studio businesses, as well as for some photofinishers that might offer identification photographs,
in addition to their main business of material sales and film developing and printing. Example 1 is a single-light
arrangement in which the placement of a panel of reflective material is used to provide more balanced lighting.
Example 2 is a two-light arrangement with a lower reflective panel providing illumination to the region under a
subject’s chin. Example 3 is the same as Example 2, but with a third light behind the subject to eliminate
shadows on the background material. Several recommendations for camera and subject positioning are also
provided below.
B.2.1.3.1 Example 1: Proper lighting arrangement with a single light
In this arrangement, illustrated in Figure B.4, a single light and multiple reflector panels are employed to
illuminate the subject’s face uniformly. The light, shown with a lamp reflector, should be placed approximately
35 degrees above the line between the camera and the subject and be directed toward the subject’s face at a
horizontal angle of less than 45 degrees from the line. A reflector panel should be placed on the subject’s
opposite side to prevent shadows on the face. As an option, an additional reflector may be placed below and
in front of the subject’s face to illuminate the area around the chin.
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Grey background
Grey background
Grey background
Grey background
ISO/IEC 19794-5:2005/Amd.1:2007(E)
Lamp Lamp
Light Light
reflector reflector
Side reflector
Less than 45º
panel
Camera
35º
Camera
Plane
reflector
Plane
reflector
Tripod
Side reflector
panel
1.2 - 2.5m
Top view
Side view
Figure B.4 — Lighting arrangement for a photo studio with a single front light
B.2.1.3.2 Example 2: Proper lighting with dual lights
In the second example illustrated in Figure B.5, two lights are employed. The lights, shown with lamp
reflectors, should be placed approximately 35 degrees above the line between the camera lens and the
subject. Both lights should be placed within 45 degrees of the line between the camera lens and the subject.
Such an arrangement softens the edge of shadows and makes the lighting on the subject more even. The
optional plane reflector in front of the subject supplies additional light around and below the subject’s chin.
Main light Main light
Lamp
reflector
Front light
Lamp
less than 45º
reflectors
Camera
35º
Camera
Plane
Plane
reflector
Tripod
reflector
Lamp
reflector
Front light
1.2 - 2.5m
Side view Top view
Figure B.5 — Lighting arrangement for a photo studio with dual front lights
B.2.1.3.3 Example 3: Proper lighting with dual lights and background lighting
The use of a background light added to the arrangement shown previously in Example 2 should eliminate
shadows visible on the background behind the face. As illustrated in Figure B.6, the background light should
be aimed at the background and be placed directly behind and below the subject.
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ISO/IEC 19794-5:2005/Amd.1:2007(E)
Main light
Lamp
Lamp Main light
reflector
Front light
reflector
30 - 45º
Camera
Camera
Plane
Back-
reflector
Plane
Tripod
ground
reflector
light
Back-
Lamp
ground Front light
1.2 - 2.5m
reflector
light
Side view Top view
Figure B.6 — Lighting arrangement for a photo studio with dual front lights and a background light
B.2.2 Recommendations for photo booths
A photo booth is typically a coin-operated, self-portrait photography unit, mostly used for taking ID pictures
and equipped with such tools as a camera, lighting, stool, plain background, printing device and monitoring
screen, and sometimes including an audio self-guidance application. Optimizing photographic technology
enabled its space-saving size, which has contributed to its widespread use around the world. Following are
some guidelines for the design and operation of such photo booths. Front, side, and top views of the
arrangements described in the guidelines are provided. Also provided in this clause are suggestions for
camera and subject positioning and a description of methods to provide feedback to the subject concerning
his or her pose and expression.
B.2.2.1 Proper lighting
⎯ Position multiple lights behind a diffuser panel and symmetrically above the camera. This will provide
even lighting on the subject’s face and eliminate most glare and shadow problems. Place a background
light low and midway between the background and the subject.
⎯ The placement of the front lights 35 degrees above the line between the camera and the subject's head
prevents direct reflection of the flash from a subject’s glasses.
⎯ The inside walls should be white, except directly behind the subject. The white walls serve as reflectors
and ensure that lighting on the face is uniform horizontally and vertically.
⎯ The interior lights of the booth should be left on during operation. This will usually eliminate red-eye
problems associated with photography in dim light.
⎯ To eliminate unwanted shadows around the chin caused by lights above the subject, direct or indirect
lighting from below and in front of the subject should be used.
⎯ To ensure that the booth is free from the effects of external light, an opaque curtain should be employed.
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ISO/IEC 19794-5:2005/Amd.1:2007(E)
B.2.2.2 Example configuration for a photo booth
Room light
White inner
walls
Lamp reflectors
Lights
Face positioning frame
Background
Adjustable height light behind
stool subject
Front view
White inner
walls Room light
About
Lamp reflector
35º
Lights
Camera
Face positioning
frame
Background
light
Revolving
Light
stool
Side view
0.7 – 1m
Less than
45º
Light
Camera
Light
Top view
Background
Lamp
light
reflector
Figure B.7 — Recommended placements of subject, camera, and lights in a photo booth
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ISO/IEC 19794-5:2005/Amd.1:2007(E)
B.2.2.3 Camera-subject positioning
Proper positioning of the subject and control of the subject’s pose can be improved through feedback provided
to the subject via a mirror or a live-video monitor.
• A display device should be installed in the booth to provide a live image of the subject on the
wall he or she faces. The device could be a one-way (half-silvered) mirror or a left-right reversed
live-video monitor. The display should contain a frame which the subject can use to ensure that
his/her entire head is fully visible, that his/her eyes are at the correct height, and that his/her face
is centered in the camera’s field-of-view. Such a frame is illustrated in the following diagram.
• A height-adjustable chair or stool should be provided to allow the subject to face the camera and
adjust his eyes to the proper height.
• Camera-to-subject distance is generally within 0.7-1.0 m.
Confirming position Confirming position Confirming position
frame example 1: frame example 2: frame example 3:
Outer indicator lines Inner indicator lines Inner indicator frame
Centre line
Centre line
Frame for
Eye Eye
face size
position position
and
line line
position
Height-
adjust-
able
stool
Mirror or video Mirror or video Mirror or video
image image image
Figure B.8 — Use of a display frame for head positioning
B.2.2.4 Adjustment of size, expression, etc. by monitor-GUI
• An image preview should be provided to allow a subject to recapture the image before it’s
printed or written to a storage medium, in case a subject might deem his/her pose or expression
unacceptable. Illustrations of acceptable poses and expressions should be provided inside the
booth.
• The size of the head in the image should be adjustable before printing or storage by allowing the
subject to identify the positions of his/her crown and chin in a preview image. The system would
then scale and crop the image accordingly. An illustration of such a preview image is provided in
figure B.9.
• Alternatively, face detection software that automatically sizes and centers the head within the
field-of-view can be used to ensure proper head positioning. Given that such software
sometimes does not determine the face position correctly, a preview image should be provided
with provision for manual override of the automatically determined position.
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ISO/IEC 19794-5:2005/Amd.1:2007(E)
A repositionable
horizontal line to indicate
the top of the head
A repositionable
horizontal line to indicate
the bottom of the chin
Figure B.9 — Use of movable horizontal lines to set head size
B.2.3 Recommendations for a registration office environment
One of the major application areas of this standard is the use in the context of identity cards and especially
Machine Readable Travel Documents (MRTDs). In this domain, images of applicants are either supplied by
the applicant or taken in a “live enrolment scenario” in the registration office. For the first case, subclauses
B.2.1 and B.2.2 apply. In contrast, this subclause focuses on the recommendations for live enrolment in a
registration office environment, where lack of space often is a major concern. Nonetheless, image quality
should be as close as possible to that achieved through the recommendations provided previously for the
photo studio or photo booth, particularly for MRTDs.
B.2.3.1 Proper lighting
In the best practice arrangement for the Registration Office Environment illustrated in Figure B.10 the subject
and the background are illuminated by two diffuse light sources that are mounted in a console with a small
footprint, so that it fits into a typical registration office environment. The console can be mounted on the floor
or on the wall. Synchronized flash type illumination should be used for these light sources to enable high
shutter speed and, thereby, avoid blur caused by a subject's motion. Direct lighting from the sun should be
prevented in the office by proper means, e.g., by using curtains or roller blinds.
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ISO/IEC 19794-5:2005/Amd.1:2007(E)

Figure B.10 — Recommended placements of subject, camera, and lights
in a registration office environment
B.2.3.2 Camera-subject positioning
• Proper positioning of the subject and control of the subject’s pose can be improved through feedback
via a second live-video monitor facing to the subject. An image preview should be provided to allow a
subject to be recaptured before the image is submitted for further processing, in case a subject might
deem his/her expression unacceptable.
• A revolving and height-adjustable chair or stool with an additional cushion for little children should be
provided to allow the subject to face the camera and adjust his eyes to the proper height.
• Camera to subject distance is generally within 0.5 to 1.0 meter.
B.2.3.3 Operator support
• Proper positioning of the subject and control of the subject’s pose can be improved through feedback
to the operator via a live-video monitor showing the face of the subject during the acquisition process.
An image preview should be provided to allow the subject to be recaptured before the image is
submitted for further processing, in case the operator might deem the pose or expression
unacceptable.
• To further improve the process and before the image is further processed, the operator should
approve the quality of the image. This can be done with the support of face image quality assessment
software, which enables checking the image automatically to ensure it fulfills the requirements of the
registration authority or the requirements and best practices provided in this standard. Clause B.5
provides further information on such software and two examples of user interfaces.
B.3 Guidelines for printing
If used for the submission of images to a face recognition system, printing of the images (by either traditional
photographic or newer digital techniques) will often be the step between acquisition and recognition that most
limits image quality. Thus, it is important that the inherent capabilities of the printing process be used optimally
to preserve the maximum amount of information in the image.
Digital printing systems can be broadly categorized into two types: (1) those that are able to control either the
density or dot size of ink deposited at each ink dot; and (2) those that can produce ink dots only of a
consistent size and density but that can change the frequency of occurrence of the dots. The first category
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ISO/IEC 19794-5:2005/Amd.1:2007(E)
can be termed continuous-tone printers, the second half-toning printers. If of sufficient resolution, either type
may be used to produce prints for scanning and submission to automated face recognition.
B.3.1 Spatial and tonal resolution trade-offs
In any printing method, there is necessarily a trade-off between spatial and tonal resolution (or intensity
gradation)—that is, a trade-off exists between the fineness of image details that can be preserved and the
smoothness of transitions between pixel levels. Ideally, a process employed for printing face images should
not limit either spatial details or tonal gradations to the extent that recognition system accuracy is diminished.
Many countries now expect to receive passport and visa photos that are approximately 50 millimetres square,
with a typical distance between the eyes of about 12 millimetres, assuming that face height is somewhat
greater than half of the picture height. To provide the 120 pixels between the eyes recommended in
Informative Annex A.3, such a photo would require scanning at a spatial sampling frequency of about
12 pixels per millimetre (300 pixels per inch). A halftone printer would need to be capable of printing about 160
dots per millimetre to preserve information at that level of spatial detail with 256 levels of tonal resolution—a
level of printing accuracy achievable today only at considerable cost. Clearly, some compromises in spatial or
tonal resolution, or both, will be required.
B.3.2 Recommended printing quality
Because the range of available printing technologies is so great, a full set of recommendations covering all
potential techniques cannot be provided in this annex. Moreover, even for any one printing technique, the
choice of paper can have a substantial effect on image quality. Therefore, the approach taken in the following
subclause is not to provide recommendations that are specific to a particular printing technology, but rather to
describe the visual appearance of the resulting prints and the minimum quality of digital images resulting from
scanning of the prints.
B.3.2.1 Resolution and posterization
Any face printing process should produce a smooth image that is capable of accurately rendering fine facial
details, such as wrinkles and moles, as small as one millimetre in diameter on the face. All flesh tones from
both light- and dark-complexioned subjects should be printed accurately and no “hot spots” or shadow drop-
out should be apparent. Smooth facial details should be rendered without posterization or contouring.
Posterization occurs when otherwise smooth details in an image are rendered as an abrupt change in printed
colour or density (i.e., as a visible contour).
B.3.2.2 Saturation
With the exception of glare or glints caused by small areas of possible specular (mirror-like) reflection, no
portion of the printed image should be saturated in white or black. In other words, no portions of the
background or the subject’s garments should be printed fully white and details should be apparent in dark
shadow regions.
B.3.2.3 Moiré or visible dot patterns
Digitization of printed photos often introduces artifacts, such as moiré, and certain printing processes can
exacerbate the generation of such artifacts. The printing process employed should not produce any noticeable
moiré pattern when its prints are scanned with a document scanner at a sampling frequency of 12 pixels per
millimetre (300 pixels per inch) or lower in each axis. If a printed photo has been produced through a periodic
half-toning process, scanning the photo will almost invariably introduce moiré. Thus, those printers, such as
inkjet and laser printers, which inherently employ half-toning to simulate continuous tones, should use non-
periodic (or dithered) half-toning methods. Furthermore, the printing process should not produce dot patterns
visible to the unaided eye.
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ISO/IEC 19794-5:2005/Amd.1:2007(E)
B.3.3 Use of a photo template
To facilitate evaluation of printed photographs, it is often useful to provide a transparent template to an
acceptance agent or other individual charged with evaluating photo quality. The template would display the
limits of head size and rotation (roll) and, when superimposed on the photo, could assist in the determination
of whether a submitted photo is compliant with the requirements. An example of such a template, provided by
Citizenship and Immigration Canada, along with instructions for its use, is reproduced (at a reduced size) in
the figure below.
Figure B.12 — Example photo template (provided by Citizenship and Immigration Canada)
B.4 Guidelines for scanning
The intent of these guidelines for scanning is to preserve, to the extent possible, all face-identifying
information present in a printed photo when it is converted to a digital image. Preserving the information in a
printed colour photo involves sampling it at a sufficient spatial frequency with adequate quantization in at least
three spectral regions, usually in the red, green, and blue regions of the spectrum.
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ISO/IEC 19794-5:2005/Amd.1:2007(E)
B.4.1 Sampling frequency and quantization levels
For a typical passport or visa photo a minimum spatial sampling frequency of about 12 pixels per millimetre
(300 pixels per inch) is required to provide about 120 pixels between the eyes. The number of quantization
levels should be at least 256 levels per colour, with three colours per pixel.
B.4.2 Spatial resolution
Spatial resolution is a measure of the ability to discern fine detail in an image and, although it’s related, it is a
metric distinct from sampling frequency. An often used measure of spatial resolution is the modulation transfer
function (MTF). To ensure fine facial details are preserved, the scanner’s MTF should be at least 20 % at a
spatial frequency of 6 cycles per millimetre. Furthermore, the scanner’s spatial resolution should be very
similar in both axes and should not be enhanced through image sharpening or high-pass filtering algorithms.
B.4.3 Output colour space
Since red-green-blue (RGB) colour space and its derivatives are inherently device-dependent, the scanner’s
output should be converted to a well-defined, device-independent colour space such as sRGB. Alternatively,
an International Colour Consortium (ICC) standard-compliant colour profile for the scanner’s native space can
be embedded within the output image file.
B.4.4 Saturation
Saturation occurs when significant numbers of pixels have values that are at the limits of quantization, i.e., at
the levels of 0 or 255, if quantization of eight bits per colour is employed. Acceptable scanned face images
should not have a significant number of pixels in saturation.
B.4.5 Image compression
To reduce scanned image files to manageable sizes, lossy image compression with JPEG or JPEG2000 is
typically used in document and film scanners. For some scanners, the manufacturer or software designer has
incorporated a single or limited number of image quality-compression ratio trade-off points that a user may
choose. The selection of overly high compression may substantially reduce image quality and, hence,
diminish the accuracy of face recognition, as described in subclause A.3.3 of Informative Annex A of this
standard. Therefore, a user must be cognizant of the available image quality alternatives offered by the
scanning system and the consequences of selecting certain quality-size trade-off points. If storage space or
transmission time for the generated images is not overly limited, an alternative offering high image quality and,
hence, large file size is an appropriate choice to ensure best possible recognition accuracy.
B.5 Face image quality assessment software
Several products, in the form of software development kits, which attempt to measure the compliance of
submitted face images with various requirements described in the body of this standard, have become
available commercially. Typically, these products provide multiple measures of face image quality, as well as
a single, combined overall quality and can determine automatically whether submitted face images are likely
to be of adequate quality for a particular application. Some of the metrics which have been incorporated into
these products include face size, face centering, contrast, focus, background texture or uniformity, lighting
uniformity, and head rotation (yaw and roll). Ideally, these metrics will correlate well with human perceptions of
quality or with automated face matcher performance and will be thresholdable at user-defined settings. Face
image quality assessment software may be a useful adjunct to human assessments of quality in photo
studios, photo booths, or registration office environments. Examples of the graphical user interfaces (GUIs) for
two such products are shown in the following figure.
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ISO/IEC 19794-5:2005/Amd.1:2007(E)

Figure B.13 — Two sample GUIs of face image quality assessment software
14 © ISO/IEC 2007 – All rights reserved

ISO/IEC 19794-5:2005/Amd.1:2007(E)
B.6 Tables of the recommendations
Most of the recommendations for scene setting, photographing, after photographing and photographic quality
are summarized in the following tables. In these tables, the Contents column contains references to the
relevant sections of this standard. The PS and PB numbers relate to the similarly labeled photo studio and
photo booth examples provided in Clause B.7, Photographic Examples.
B.6.1 Scene setting
Table B.1 — Scene setting Recommendations
Category Contents Photo studio Photo booth Registration office
Number of lights Use 2 or more lights, if possible. Use 2 or more lights, if possible. Use 2 or more lights. If
When a single light is used, When single light is used, white possible, background
(ref. 7.2.10 Hot spots)
employ reflectors to redirect the walls that can serve as reflectors lighting is recommended to
light. Background lighting is are recommended. Background reduce shadows on
recommended to reduce lighting is recommended to background.
shadows. (PS1) reduce shadows. (PB1)
Lighting methods Provide diffuse illumination by Provide diffuse light using lamp Provide diffuse light using
using lamp reflectors ( ex. reflectors or a white translucent white translucent plastic
(ref. 7.2.10 Hot spots)
bounce umbrella), lamp plastic panel. White walls can panel for down and up
diffusers(ex. soft box strobe), also serve as reflectors. light.
reflector panels, etc. (PS2)(PS3) (PB2)(PB3)
Colour temperature 4500 – 6500K is recommended. 4500 – 6500K is recommended. 4500K – 6500K is
Hold colour balance using grey recommended. Hold colour
or white walls. Eliminate stray or balance using grey or
outdoor light with a curtain or white background.
door. Minimize outdoor light by
using appropriate means
(e.g. curtains).
Guide Number of Recommended Guide Number Guide Number should be over 7. Guide Number should be
strobe is over 7 for external flash, 14 (photographic distance of 0.7 – over 10 (photographic
Lighting
for built-in flash. (photographic 1.0 m) distance of 0.5 – 1.0 m).
distance of 1.2 – 2.5 m) The Use two balanced strobes.
built-in flash in compact
cameras is not recommended
because the Guide Number is
typically only about 10, so it is
insufficient, and it produces bad
lighting (e.g, shadows on the
background and red-eye)
Lighting Uniformity Lighting should be evenly Lighting should be evenly Lighting should be well
distributed. The difference of distributed. The difference of balanced. The difference
(ref. 7.2.7 Subject and
four exposure values on the left four exposure values on the left of four exposure values on
scene lighting)
and right sides of a face, chin and right sides of a face, chin the left and right sides of
and forehead should be less and forehead should be less the face, chin and
than 1 EV. (PS4) than 1 EV. (PB4) forehead should be less
than 1 EV.
Light arrangement 30 – 45 degrees of subject-lens Symmetrical position. 30 – 45 Above and under the
axis. 35 degree elevation angle degrees to subject-lens axis. 35 subject-lens axis. Typically
for subject-light line. (PS5) degree elevation angle for 15° degrees from above
subject-light line. (PB5) and 45° degrees from
below.
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ISO/IEC 19794-5:2005/Amd.1:2007(E)
Category Contents Photo studio Photo booth Registration office
Pose angle Provide simple guidance to the Guide the proper position of the Provide simple guidance to
subject concerning the proper face for the subject. Position the subject concerning the
less than +/- 5
pose. Position camera camera horizontally on the proper pose. Camera
degrees）(ref. 7.2.2
horizontally on the centre line of centre line of the face, vertically position meets horizontally
Pose)
the face, vertically between the between the eyes and the tip of right at the centre line of
eyes and the tip of the nose. the nose. The height adjustment the face, vertically between
Camera height adjustment may can be done with a revolving eyes and the tip of the
be done with the tripod. (PS6) stool for the subject. The subject nose. The height
can also check the proper adjustment can be done
position by a mirror in front of with a revolving stool for
him/her or by a preview image the
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