Fingerprint Sensor Question!

I've had my 5S for two weeks now, and I did have a query about the fingerprint sensor, and how I use it.

I've noticed from the get go that the fingerprint sensor worked in a very hit and miss manner for me. I took this to be attributed to the fact that I have very dry hands, and that the skin on my thumb is dry enough at times that is has trouble reading my print.

Also, at the same time I am rather used to pushing the home button with the tip/forward edge of my thumb, rather than placing my thumb flat on the home button (it's just easier for me that way, I guess because of how I hold the phone). It's worth noting that I awake the phone my pushing the unlock button on the top of the phone, and then place my thumb on the sensor. My thumb typically doesn't not come into contact with the ring around the home button ...

So between the dry skin, and the use of the tip of my thumb versus the flat of my thumb I thought I might just disable the fingerprint lock.

So, now as of this morning I realized that maybe my thumb needs to touch part of that ring around the home button. I've tried it several times, and am unsure if it is imagination or not; but it works great now that I make sure my thumb touches the ring around the home button when unlocking the phone.

Does this ring actually help the phone read my fingerprint? I'm hesitant to think it activates the print scanner because even when just use the tip of my thumb without touching the ring the phone says "try again." I could be mistaken though.

Sorry for the long post! Thanks!
Loving the 5S!