How to use flash and not get a black background

Nikon D5, Sigma 24-105mm f/4 DG OS HSM Art Lens, ISO 10000, ƒ/5.6, 1/10 – Nikon SB-900

One of the most difficult things to shoot for many beginners in photography involves shooting in a very dark location with a flash.

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

The trick is to set the camera as if you were shooting without a flash which is to use a high ISO. Here I set the camera to ISO 10000. Then the flash was set to fire on TTL slow shutter sync. This means the flash fires immediately at a extremely fast duration and then the shutter stays open longer.

Nikon SB-900 Flash Duration

1/880 sec. at M 1/1 (full) output
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 

With 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.

Nikon D5, Sigma 24-105mm f/4 DG OS HSM Art Lens, ISO 10000, ƒ/5.6, 1/5 – Nikon SB-900

 Now notice as they walk from the church where the lights in the background are still impacting the exposure to the car the scene is getting darker. We have moved from 1/10 to 1/8 and then finally shooting at 1/5 to get the background to show up.

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.