Basia Nasiorowska 

Interoptic Networks CC 

basia@interoptic.co.za 

Cell: +27 82 733 0030 

Tel: +27 11 805 1075 

Fax: +27 11 805 0798 

15 March 2010 

Facial Recognition Identification Testing Utilizing Still and Live Twin Children 

Face Images 

By BASIA NASIOROWSKA 

Interoptic Networks CC 

Tel: 011 805 1075 

Cell: 082 733 0030 

basisa@interoptic.co.za 

Topic Area I: Test Methods: 

Product and component tests; Identification systems 

Abstract 

This abstract will give a brief overview of the testing, methodologies and observations. 

This project was undertaken in order to develop methods and ways to test Facial Recognition 

Identification and Verification products. A unique face database of twin children has been created as 

well as live testing of Facial Recognition products is conducted on a yearly basis since 2004. 

The approach was undertaken to obtain photographs of different sets of twin children located in South 

Africa over a minimum period of five years, with an extension to ten years, as well as conducting live 

operational testing of facial Recognition products once a year. 

This face database has the following properties: 
 Twin siblings 

 Ageing 

 Varying ethnicity 

These aspects are critical when analyzing the quality of face recognition products as they deal with three 

of the most concerning issues surrounding face recognition. 

Before face recognition was ready for industrial application, the issue of varying ethnicities was the 

major concern for researchers and developers. This problem has since been solved, and skin tone no 

longer plays a role in the success rate of recognition algorithms, including those which make use of 

visible light only. A face database of ethnic twin children was however not available. 

Since the maturity of face recognition technology, two new concerns were raised. For the general 

public, ageing in face recognition systems is an issue and a critical measuring stick for the evaluation of 

face recognition systems. Despite the prevalence of face databases available, none include sufficient 

ageing and none include the ageing of young children. 

Another aspect of ageing in children is being able to find children who have gone missing. Recognizing 

such children would only be possible if the system had recently added a reference image of the child and 

a probe image from years before. It is expected that a human would struggle to identify people in such 

scenarios and the ability of face recognition systems to do so is to be tested in this project. 

The issue of twins originated due to security issues, for example at a bank where there might be twin 

siblings making use of the same branch. Would the system be able to tell them apart? Furthermore, 

would the system be able to differentiate between non-twin siblings that look alike or even members of 

the general population that might look alike? The questions of non-twin siblings and general populous 

look-alikes are obviously obsolete when set aside the issue of twins and leads to the desire for a twin 

sibling face database. 

Testing 

A static, image-to-image facial recognition system was tested as a goal for this project. It should thus be 

considered that all results in this document are directly linked to the accuracy of the algorithm and 

implementation thereof in the chosen application. 

Methodology 

The subjects 
The database is comprised of twenty (20) members, each a member of a set of twins, eight (8) of 

identical twins and two (2) pairs of non-identical (fraternal) twins, in this case boy-girl pairs. At the 

commencement of the project during 2004, the youngest of the 10 pairs were five (5) years old, turning 

six (6), and the eldest were twelve (12) turning thirteen (13). 

During the various image collection attempts, the resolution of images was not held consistently, 

causing discrepancies in the yearly image resolutions. This also has consequences in the training times 

and general results. 

Testing 

Various tests were conducted using the Twins database as a reference, simulating real life scenarios. 

 General ageing: images from 2005 used to probe a database trained with images from 2004, etc. 

 New reference images with old probe images: 

Images from 2005 used to probe a database trained with images from 

2006 etc 

 Duplicate analysis: Determining whether or not the systems can differentiate between the 

twin siblings. 

Research and Analysis 

General Observations 

The images were received in different resolutions; the images from 2004 were 640x480, while the 

images from 2005 and 2006 were in much more detail (3072x2304). The images from 2005 and 2006 

were thus resized to 640x480, to ensure an accurate test. 

During the testing the program responded almost immediately when doing enrolments and 

recognitions. There is thus no timing information in the results. 

Table 1: General observations 

Number of Images Dimensions (in pixels) Average size if file 

2004 20 640x480 140 kB 

2005 20 640x480 170 kB 

2006 18 640x480 167 kB 
 Number of images: The number of images from each year. ‘20’ indicates a full complement of 

images. 

 Dimensions: The resolution of that year’s images, in pixels. 

 Average size of file: Average memory occupation of each image file in the corresponding year. 

When testing facial recognition the issue of background noise is critical. Consistency of image colour 

and quality should be relatively similar throughout databases (this cannot always be the case, but when 

photographs are taken in controlled conditions, it should be possible). Table 2 shows a breakdown of 

the quality of images used in the twin database. 

Table 2: Image Quality & Background Noise 

Year Colour Consistency 

Background 

Colour Texture 

2004 Inconsistent: Brown lighting & 

blue lighting 

Grey (9/20) 

Brown (11/20) 

Plain, wrinkled 

2005 Consistent Grey Plain 

2006 Consistent Grey Plain, wrinkled 

From Table 2 it is clear that the images captured in 2005 are most suitable for recognition purposes, 

while the images from 2006 are of sufficient quality to be used in such tests. The images from 2004 are 

however, problematic, with inconsistent lighting throughout and a wrinkled background. The fact that 

these images are less suitable for this type of test is confirmed in the results throughout. 

Basia Nasiorowska 

Interoptic Networks CC 

basia@interoptic.co.za 

Cell: +27 82 733 0030 

Tel: +27 11 805 1075 

Fax: +27 11 805 0798