Why confidence = 0 when two images are identical?

[tomsiu]

Hello, may I enquire why when two identical images are compared, the confidence will show 0 ?

confidence = number of inliers / (8 + 0.3 * number of matches)

For two identical images, suppose both inliers and matches should be the same, and the matches should be very large?

What is the largest value supposed the confidence can be?

Thank you.