Enabling High-Speed Flash (Auto FP) on the Nikon D7200
To properly expose flash pictures, the Nikon D7200 camera has to synchronize the timing of the flash output with the opening and closing of the shutter. On the D7200, this synchronization normally dictates a maximum shutter speed of 1/250 second when you use the built-in flash.
But by enabling Auto FP flash, you can bump the maximum sync speed up to 1/320 second for the built-in flash. If you attach a compatible Nikon flash unit, you can access the full range of shutter speeds.
When Auto FP flash is used, the flash fires a little differently. Instead of a single pop of light, it emits a continuous, rapid-fire burst while the shutter is open. Although that sounds like a good thing, it actually forces a reduction of the flash power, thereby shortening the distance over which subjects remain illuminated. The faster your shutter speed, the greater the impact on the flash power. So at very high speeds, your subject needs to be pretty close to the camera to be properly exposed by the flash.
Because of this limitation, high-speed flash is mostly useful for shooting portraits or other close-up subjects. In fact, it’s very useful when you’re shooting portraits outside in the daytime and you want the background to appear blurry. One way to get that blurry background is to use a low f-stop (wide aperture). Problem is, a wide aperture lets a ton of light into the camera, and at a shutter speed of 1/250 second, all that light typically overexposes the picture even at ISO 100. With high-speed flash, you can increase the shutter speed enough to compensate for the large aperture.
To access the high-speed flash option, open the Bracketing/Flash section of the Custom Setting menu and select the Flash Sync Speed option, as shown. You can choose from the following settings:
1/320 s (Auto FP): At this setting, you can use the built-in flash with shutter speeds up to 1/320 second. For select Nikon flash units (including models SB-910, SB-900, SB-800, SB-700, SB-600, and SB-R200), you can use any shutter speed.
1/250 s (Auto FP): For compatible external flash units, the high-speed flash behavior kicks in at shutter speeds over 1/250 second. With the built-in flash, the flash sync speed is set to 1/250 second. In P and A exposure modes, the high-speed flash sync is activated if the camera needs to use a shutter speed faster than 1/250 second. (Note that the camera may sometimes use a shutter speed faster than 1/250 second in those modes even if the shutter speed readout is 1/250.)
1/250 s to 1/60 s: The other settings on the menu establish a fixed maximum sync speed. By default, it’s set to 1/250 second, and high-speed flash operation is disabled.