Volume up/down for pictures?

[learninmypc]

I was out taking picture with my iPad today & couldn't hear the familiar "clicking" sound it makes so I turned the volume up & it took several pics, pushing it the other way did same. I had 20 some pics I had to delete. Since when is the volume switch used for taking pics???

 

[learninmypc]

The long horizontal bar is the volume up & down.

 

[learninmypc]

I found out the same thing happens on my iphone 4(s) Hmmmm

 

[learninmypc]

Oddly enough there is nothing in the manual about this(n) .that I can see.