This option controls flash sync speed.
Fixing Shutter Speed at the Flash Sync Speed Limit
To fix shutter speed at the sync speed limit in mode S or M, select the next shutter speed after the slowest possible shutter speed (30 s or %). An X (flash sync indicator) will be displayed in the viewfinder and control panel together with the flash sync speed.
Auto FP High-Speed Sync
Auto FP high-speed sync allows the flash to be used at the highest shutter speed supported by the camera, making it possible to choose the maximum aperture for reduced depth of field even when the subject is backlit in bright sunlight. The information display flash mode indicator shows “FP” when auto FP high-speed sync is active.
Auto FP High-Speed Sync
When 1/320 s (Auto FP) or 1/250 s (Auto FP) is selected for Custom Setting e1 (Flash sync speed, 0 e1: Flash Sync Speed), the built-in flash can be used at shutter speeds as fast as 1/320 s or 1/250 s, while compatible optional flash units can be used at any shutter speed (Auto FP High-Speed Sync).
| Shutter speed | 1/320 s (Auto FP) | 1/250 s (Auto FP) | 1/250 s | |||
|---|---|---|---|---|---|---|
| Built-in flash | Optional flash unit | Built-in flash | Optional flash unit | Built-in flash | Optional flash unit | |
| From 1/8000 to but not including 1/320 s | — | Auto FP | — | Auto FP | — | — |
| From 1/320 to but not including 1/250 s | Flash sync * | — | Auto FP | — | — | |
| 1/250–30 s | Flash sync | |||||
Flash range drops as shutter speed increases. Flash range will nevertheless be greater than that obtained at the same speeds with Auto FP.