When using flash, shutter speed does not affect the subject's flash illumination. Shutter speed affects the ambient light. Aperture affects the flash illumination (along with ISO, distance and power setting). Balance ambient to flash with aperture
When using flash, shutter speed does not affect the subject's flash illumination. Shutter speed affects the ambient light. Aperture affects the flash illumination (along with ISO, distance and power setting). Balance ambient to flash with aperture