FOCUS MODESThe advanced autofocus system of the F4 works even underextremely low-light conditions - as low as EV minus 1. TheElectronic Rangefinder operates for both autofocus andmanual focusing. Manual focusing can also be accomplishedusing the clear matte screen or any optional screen with anoptical rangefinder. Normally, the Electronic Rangefinder's abil-ity to detect focus is superior to the human eye. However, thereare certain subjects that cannot be focused upon in any way -such as shiny metallic subjects, blank walls, etc. In this case, Xappears and autofocus with an alternate subject at the samedistance or manual adjustment by estimating the distance isrecommended.Manual Focus with Electronic RangefinderManual focus using the Electronic Rangefinder works with mostNikon lenses, including AF Nikkor when operated manually.(For a complete list of usable lenses, see lens compatibilitychart, page 86.) Lenses with a maximum aperture slower thanf/5.6 are not suitable for Electronic Rangefinder focusing, eventhough focus indicator LEDs appear. Focus using clear mattefield or change focusing screen to J type.321. Set focus mode selector to M (manual). If lens has an A-Mswitch, set to M.2. Look inside viewfinder and position focus brackets on themain subject.Lightly press shutter release button.