You know there are several ways to attack this, one expensive and labor intensive and one very inexpensive and labor free.
Just depends on what you want.
The first method is to build up the lower flooring with a subflooring then your top floor, if you will. This means raising the lower floor even with the higher floor. Floor levelor is not meant to be used to gain this much height, so a new sub floor is my best thinking at this time.
The second method is a nice transitional threshold piece that joins the two different height floors and bridges them. You will not see the change in height, but your foot and balance will notice the 1/2 inch difference when crossing the bridge area.
You can get this peice at any home center and it comes in many colors. You actually nail this down to the floors.
Check it out, its an inexpensive fix.
Others will surely address other methods that they have used that are both intensive and not so.