April 26 2005

NIST Fingerprin

NIST Fingerprin

Image Quality Image Quality

and relation to P

and relation to P

Elham Tabassi

Image Group – NIST
April 26 2005

quality is important ... quality is important ...

• The performance of a fingerprint mat

affected by the quality of fingerprint iand present in the database. 

• In FPVTE “many types and characteristic

were analyzed; the variables that had thon system accuracy were the number of fingerprint quality fingerprint quality...Poor quality finge

reduced accuracy”.

• If the quality of the fingerprint images is 

system's identification performance is reduced.
April 26 2005

... and 5 reasons why and 5 reasons why 

knowledge of biometric sample quamatching can be used to improve tand performance of a biometric syste

• if we can perform real-time quality asses

- we can prompt to recapture samples of insuff- improve reference database integrity 

• process samples differently based on the

- poor quality samples can be processed 

algorithms or thresholds

• cause higher quality sample dominate fu• collect relevant statistics

- correlation among fingers- compare capture devices and/or environment
April 26 2005

NIST Fingerprint Image Q(NFIQ)

NIST Fingerprint Image Q(NFIQ)

• NFIQ number is a prediction of 

performance; it reflects the predictivnegative contribution of an individual soverall performance of a fingerprint matc

• NFIQ’s 5 levels of quality are intended to 

of the relative performance of a mfingerprint matching system.

• NFIQ=1 indicates high quality samples, 

and/or FNMR is expected.

• NFIQ=5 indicates poor quality samples, 

and/or FNMR is expected.
April 26 2005

NFIQ

NIST Fingerprint Image Q

NIST Fingerprint Image Q

feature neural 

extraction network

feature extraction: computes appropriate sifidelity characteristics and results in an 11-dvector.neural network:classifies feature vectors intquality based on various quantiles of the norscore distribution.quality number: an integer value between 1(poorest).
April 26 2005

NFIQ and performance NFIQ and performance

FAR

TAR

e

qn

NFIQ

excellent quality samples result inhigh performancpoor quality low performance
April 26 2005

poor quality samples poor quality samples

distorted source e.g. scars on a fingertip

nfiq=5

distortion in one or more steps of the process e.g. capture or compression

nfiq=5

ltsaqmmTlz
NFIQ effectiveness NFIQ effectiveness 

• evaluation criterion is rank ROC as a funct

quality

• used various fingerprint matching algorithm

datasets to evaluate NFIQ

- 15 different COTS fingerprint matching algorith- 22 different datasets of different fingers captur

and at different operational settings

- each test dataset has 2 fingerprint images of 60

• compared (TAR,FAR) of levels of quality at 

- as quality degrades, true accept rate decreases 

FAR increase for some.

• levels 2,3,4, and 5 are statistically separab• It takes about one third of a second to com

flat fingerprint image.
Vendor F – VISIT_POE – Right inde

threshold=350 (far,tar)=(0.012,0.

1

2

3

quality

FAR

TAR

excellent

0.0037

0.997

veryGood

0.0083

0.994

good

0.0131

0.993
April 26 2005

separable levels of qua

separable levels of qua

For each quathrough 5, w95% confidencTARs @ FAR=0.matchers aoperational daNFIQ levels 2,3statistically sep
public release public release 

• subject to US export control law• the first and only publicly availa

fingerprint quality assessment a

• technical report NISTIR-7151

fingerprint.nist.gov

1

9

OCTOBER
April 26 2005

NFIQ and PIV NFIQ and PIV

“The procedure [for the collection of finNFIQ to guide a real-time quality reacquisition of the images.”SP 800-76 Biometric Specification for Verification

• If the images of the two index fingers and 

do not all have NFIQ values of 1,2, or 3, reup to three more times.

• If unsuccessful after four acquisitions then 

repeated set that has the highest number NFIQ values of 1,2,3 or 4.

• NFIQ values for each finger shall be specif

record.
April 26 2005

conclusion conclusion

• a novel definition of fingerprint im• it works as a rank statistic for perf

all -330 combinations - of COTS finmatchers and operational datasets 

• NFIQ can be used for real-time qua

assessment

• all government agencies shall use 

the quality of fingerprints for PIV c

• will be used by FBI to assess qualit

plain impression transactions (May 

• NFIQ is publicly available but subje

export control laws
April 26 2005

thanks

elham.tabassi@nist

elham.tabassi@nist

301 975 5292 301 975 5292
April 26 2005

extra
fingerprint matching alg

fingerprint matching alg

fingerprint 

matching algorithm 

a higher similarity scores construed to indiclikelihood that the samples come from the sindividual.
April 26 2005

Statement of perform

Statement of perform

4 36 68 100 132 164 196 

0.000.050.100.15 m atch sc

non m atc

sd29 - vtb m atch and non m atch scores histog

nom

mat

poor

exce

the quality measure should be indicative of the the histogram of match scores is separated froof non-match scores.
April 26 2005

pair-wise quality wise quality

when the enrollment sample is of good qbetter than that of the use phase (searchsearch sample’s quality is sufficient to pperformance.