|Nikon D5, Sigma 24-105mm f/4 DG OS HSM Art Lens, ISO 10000, ƒ/5.6, 1/10 – Nikon SB-900|
Cameras will pick the lowest ISO when you use a flash as their default. What happens is then the background is black and the subject is well exposed at best. However in the case of this wedding photo the couple is walking out into the dark being back lit.
|Nikon D5, Sigma 24-105mm f/4 DG OS HSM Art Lens, ISO 10000, ƒ/5.6, 1/8 – Nikon SB-900|
Nikon SB-900 Flash Duration
1/880 sec. at M 1/1 (full) outputWith my choice of ISO 10000 the flash on TTL was probably firing at 1/16 power or less. So this is why in the photo above of the couple walking there is a blur around them due to the shutter being open for 1/8 sec yet the flash froze them at about 1/10000.
1/1100 sec. at M 1/2 output
1/2550 sec. at M 1/4 output
1/5000 sec. at M 1/8 output
1/10000 sec. at M 1/16 output
1/20000 sec. at M 1/32 output
1/35700 sec. at M 1/64 output
1/38500 sec. at M 1/128 output
|Nikon D5, Sigma 24-105mm f/4 DG OS HSM Art Lens, ISO 10000, ƒ/5.6, 1/5 – Nikon SB-900|
If you want to be sure you show where your subject is for reference then use slow shutter speed sync with the ISO set to where you could make photos without the flash.