Failure to use a flash outside is one of the biggest mistakes many people make with their vacation photos … with any photos. Surprisingly, pictures of people at the beach are prime candidates for flash. It’s usually so bright that the only way for your subjects not to squint is to be sure the sun is behind them. Unfortunately this creates dark shadows on their faces.
You can use your flash to fill in the shadows and make it easier to see their faces. There are limits to this working effectively. Most flashes built into cameras work best when the subject is three to ten feet away. If you get much further away your flash will have little impact on the photo. Flash fill can also improve strongly side-lit faces. This technique softens the contrast between the shadow and sunlit sides of faces.
Instead of using the built-in flash on your camera, you may opt to use a more powerful hot-shoe flash. While this may give you a few more feet of distance from the subject, there are still limits. One is the light fall off from the flash to the subject: the inverse squared law of physics. It dictates that every time you double the distance between the light and the subject the amount of light reaching the subject is cut by one fourth. In practical terms that means if you're too far away from the subject your flash will not be powerful enough to illuminate the shadows.
When it comes to using flash outside with the sun, the general rule with built-in and hot-shoe mounted flashes is: stay close. Seven to ten feet is the limit for most built-in flashes and maybe up to 20 feet with a very powerful hot-shoe flash. Sunset or dusk are other times when using a flash can improve your photos at the beach. Using flash to balance the exposure between your loved ones’ faces and the stunning sky behind them can help capture the beauty of your vacation location.
While using flash is a great way to improve your outside photos, another helpful hint is to compose your picture of the background before putting your subject (family, friend or pet) in the frame. For example if you’re in Washington, DC, compose your photos so you can see an entire monument in the background. Then leave a little extra space to one side or the other to have your friends walk into the photo facing the camera. Position them close to the camera with the monument over their shoulders in the background. Your friends will typically be seven to 15 feet away, with the monument almost a football field away from you.
Improve your vacation photos by using flash outside when your subject is closer than ten feet and composing for your backgrounds to show where you went.