I was using the DVX for the first time.. I used it for 3 hours and it was fine.

It was still fine for the next 2 hours, but on the display where the initals STD.

What does it refer too?

And how to shut it off, or manipulate it?

thank u.

Did you check the manual for it?

If it is in the lower left hand corner of the display, then the initials 'STD' means the standard auto iris control is on, as opposed to 'SPOT' or 'BACK'

Check page 47 of the manual.