The table below gives an indication which similarity threshold corresponds to which
FAR (False Accept Rate). Please note that the dependance between threshold
and FAR may be dependent on factors such as scanner type, etc.
The below numbers were obtained on a sample database with 200000 non-corresponding
fingerprint pairs. Fingerprints were acquired with an optical 500 DPI scanner.
Similarity scores returned by this library are normalized. More precisely, approximate relationship between similarity score
and False Acceptance Rate (sometimes called also False Match Rate) is given by the following formula:
similarity score=-10*log_10(FAR)
Please note that the normalization formula is only approximation. Score distribution can vary depending on various factors
such as scanner surface area, finger placement, finger quality, finger positions (index fingers tend to give higher scores
compared to little fingers, etc..)
Following numbers are valid for ANSI ISO SDK:
till version 1.58 (including)
FAR: 1% (1:100) Threshold: 9500
FAR: 0.1% (1:1.000) Threshold: 11600
FAR: 0.01% (1:10.000) Threshold: 13700
FAR: 0.001% (1:100.000) Threshold: 15650
FAR: 0.0001% (1:1.000.000) Threshold: 17700
version 1.60 till 1.64
FAR: 1% (1:100) Threshold: 8
FAR: 0.1% (1:1.000) Threshold: 19
FAR: 0.01% (1:10.000) Threshold: 40
FAR: 0.001% (1:100.000) Threshold: 85
version 2.0.0 and 2.0.1
FAR: 1% (1:100) Threshold: 20
FAR: 0.1% (1:1.000) Threshold: 35
FAR: 0.01% (1:10.000) Threshold: 50
FAR: 0.001% (1:100.000) Threshold: 65
version 2.0.2 till 2.x
FAR: 1% (1:100) Threshold: 20
FAR: 0.1% (1:1.000) Threshold: 30
FAR: 0.01% (1:10.000) Threshold: 40
FAR: 0.001% (1:100.000) Threshold: 50