Fingerprint, face or card - and why factories often need two
Fingerprint readers are the cheapest reliable option and work well in offices. On a shop floor they are frequently the wrong choice, and the reason is simply the condition of workers' hands. Oil, cutting fluid, cement dust, dry cracked skin and abraded ridges all defeat optical fingerprint sensors, and the result is a queue at shift change and a supervisor manually marking attendance.
Face recognition avoids contact entirely and has become the default for industrial attendance. It handles dirty hands, works through most safety gloves being worn, and is fast enough that a hundred workers can clock in without a bottleneck. It does need thought about mounting height and backlighting - a terminal facing a bright doorway will struggle, and the same unit moved two metres will work perfectly.
RFID cards remain useful as a fallback and for contractors and visitors, where enrolling biometrics is impractical. In practice many Bhiwadi factories run face recognition as the primary method with cards as backup, which also solves the enrolment problem for temporary labour.