How to Adjust Exposure for Ambient Light

Getting the correct exposure is one of the key elements of a great photo. The exposure triangle has been made easy by modern DSLR cameras that help you choose the right settings, but when you add a flash to the mix, things get a bit trickier. Mark Wallace has a short video on exactly this subject:

Exposure Triangle

Under normal circumstances, you need to take into account the three elements of the exposure triangle:

  1. ISO
  2. aperture
  3. exposure time (i.e., shutter speed)

When you use a flash for your photo, the triangle gets a bit more complicated.

The flash’s exposure triangle is: ISO, aperture, and flash output. The flash output goes hand in hand with the ambient light, and you should control both in order to have perfect results.

Adjusting Exposure for Flash and Ambient Light

In Wallace’s first photo, his shutter speed was 1/180 of a second, his aperture was at f/4, and the ISO at 200. Using these settings, the ambient light was just about nonexistent.

adjust ambient light high shutter speed

The initial photo, taken with a high shutter speed without flash, shows that very little ambient light is showing up on the exposure.

Turning on the flash, however, made all the difference, but the photo looked just like a small digital camera’s flash was on.

flash without adjusting for ambient light

The background is being lit by the flash, rather than ambient light, resulting in a bright, unnatural looking subject.

Slowing down the shutter to 1/12 of a second to account for the ambient light, the photo was totally different—and much better. Now you can see the background clearly, and the light from the flash is a closer match, which is much more flattering for the model.

adjust ambient light low shutter speed

The final image, taken with the exposure triangle in mind and with a lower shutter speed

What you should learn from this video is that the shutter speed affects your ambient light, and experimenting with different settings with the camera and flash will help you reach the best results.

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