Where is on-screen modifier for constraining Depth of Field tilt-shift lines?

[DavidHoch]

I’m trying to to use the tilt-shift mode in the Depth of Field blur filter in Photo for iPad, but can’t find or figure out how to enable the on-screen constrain modifier so the tilt-shift lines don’t rotate.  Can someone please explain how to do this?

Thanks,

David

[DM1]

Tap the small white triangle at the side of the bottom context menu and tap and hold 'constrain' button while adjusting settings.

You will also need to have On screen Modifiers turned on in Settings Interface panel.