III. DISCUSSION 17C. Fn. 5 controls the AF-assist beam. The three choices are ON, OFF and fire only theexternal flash.C. Fn. 6 controls whether manually-adjusted exposure level increments are in 1/2 or 1/3stop units.C. Fn. 7 enables the mirror lockup function. When C. Fn. 7-1 i selected, the mirror locksup when the shutter button is pressed completely. The shot is taken when the shutterbutton is released and then pressed completely again. The maximum mirror lockupduration is 30 seconds, after which the mirror returns.C. Fn. 8 controls whether the E-TTL II autoflash system operates in its evaluative mode orits averaging mode.Finally, C. Fn. 9 determines whether the built-in flash or an accessory Canon EX-seriesSpeedlite is synchronized to fire after the first shutter curtain completes its travel or justbefore the second shutter curtain begins to move.MenusThe Digital Rebel XT camera has ten new menu items compared to the EOS DigitalRebel camera, so a fifth menu column has been added to accommodate this newabundance of choices. Menus one and two are for image recording functions and arecolor-coded red. In menu one, the user chooses recording quality, red-eye reduction,warning beep, AF mode, metering mode and ISO speed. In the Creative Zone modes,menu two is displayed. It contains auto exposure bracketing, flash exposurecompensation, white balance, white balance shift/bracket, custom white balance,color space and parameters.Menu three is color-coded blue and has 5 playback items: image protect, image rotate,print order, auto play and review time control.Menus four and five are for camera setup functions. Theyare colorcoded yellow, with 7 items in each. Setup one hasauto power off timecontrol, auto rotate, LCD brightnesssetting in 5 levels, date/time, file numbering, format andshoot without card. Setup two has a choice of 15 differentmenu languages, a choice of video systems for playbackthrough a connected TV monitor, data communicationpreferences (Normal or PTP), custom functions, a clearsettings command, a sensor cleaning setting tha locks up the mirror and opens theshutter, and a firmware version readout. For quicker access to key camera settings,the EOS Digital Rebel XT also features a new "Quick Menu" function. When the camerais set for picture taking, the cross keys on the back provide instant access to AFmode, metering mode, white balance settings, and ISO speed. All in all, the menusettings enable Digital Rebel XT users to modify the camera’s performance accordingto their diverse applications and needs.