Facial recognition – Given the context, should the user be made aware of the process?

We are designing an application for iPads that are stationed in tech support areas. We have implemented a facial recognition capability, so that when you tap a button it begins analysing your face and if after 3 seconds it can not recognise you, the option to login in with your username will appear.

One suggestion was to use a Face ID animation which indicated your face was being analysed, however another suggestion was that the fact the user's face is being scanned should be kept hidden and as a secret since this looks more impressive.

I'd love to gather some opinions on how to approach this.