I have shot over 70 weddings using F4 or F5 with 35 - 105 lens, SB-24 or SB-25 on a Stroboframe bracket. I have found that you can tilt the flash downward just a little, and also turn the flash just slightly (left or right) to line up the IR beam with the central AF sensor to get the auto focus assist light to work. When you switch from horizontal to vertical, you have to line up the beam again. Should also work with the N90. Hope this helps. Bob Ennis
