RX100 double photos - can't find in manual

Hi All

When I take a photo of people with the RX100 I sometimes get a second photo stored which appears to be a cropped photo of the original with the face recognition portion .

I'm presuming it has to do with face recognition and I think it is when using with intelligent auto but

1) I don't seem to be able to replicate it at will and

2) I thought I'd read the manual but I can't find any reference to it now.

I have tried to search in the forum and the web but I can't find any reference that fits.

Can anyone explain the function please?

Thanks

Alan