Combining Flash with Natural Light: The Mystery Unraveled

As a photographer I am always seeking ways to either learn new things, or to refine what I already know. For many years I shot mostly natural light subjects which included people. Natural light is of course a great source of light and when used to its fullest capabilities it can create some amazing images.

A few years ago, after observing other photographers create amazing images using off camera speedlights or flash, I took it upon myself to learn how to apply that kind of lighting to my photography. The results have been eye opening. For too many years I was afraid to use speedlights because I simply did not understand how to use them. Once the lightbulb came on inside my head, I suddenly realized the potential impact using an artificial source of light can have on my photography.

Naturally, and to some degree by default, I began to combine natural and artificial light. The experience has been phenominal, because by using an off camera flash, you can in essence control the natural ambient light as well.

Here are two similar images. One was taken using natural light only. The other using an off camera flash.

Natural Light Only

Using an off camera flash

They both have certain merits to them, however, you should notice how the background light in the natural light shot appears somewhat brighter than the other one where the background light is darker. Let me explain why.

In the first natural light image, the exposure was set for the model's face so it would be correctly exposed. Because she was in a shaded area, the resulting exposure caused the background light to be somewhat over-exposed causing it to appear brighter. When shooting in just natural light, your exposure is based on both the aperture and shutter speed settings along with the ISO and it will affect all levels of the lighting. If you expose for the background, then the model will be under exposed, expose for the model and the background will be over exposed. This is rather straight forward and simple to grasp.

In the second image where we used the off camera flash, what happened is when using a flash your exposure in essence becomes a two part choreographed process. You actually have the ability to affect two different levels of exposure in the sme image. The exposure for the flash is actually controlled by the aperture setting and the ambient background exposure is controled by the shutter speed. The reason this happens is because the flash from the speedlight fires for a very short period of time, something in the range of 1/2000th of a second...it varies with the unit..and it is syncronized with the operation of the shutter. If your shutter speed is, lets say 1/200th of a second, it is 10 times slower than the flash duration, so the flash fires much more quickly than the shutter can open and close. Also understand that the Power of the flash is simply a measure of time and not the intensity of the light. In other words, if you set the flash to 1/4 power, the brightness of the flash is the same as it is when set at full power, it just stays on for a shorter period of time. But, it is still faster than the opening and closing of the shutter.


Shoot the image at 1/50th of a second or 1/200th of second lets say at f/5.6, the exposure created by the flash in essence will not be changed. Your subject will still be exposed correctly, however you can now set the ambient background exposure to cause it to be darker or even brighter.

Okay, now think about this. Why is this important? Because you can set a separate exposure value for the background, without really affecting the exposure coming from the flash on your subject, you now have almost unlimited control over your composition. By simply expanding your creative thinking, you can create some fantastic moody images where the background becomes a stronger supporting element in your portrait, indoors or outside.

Trust me, it's not all that complicated. Just remember you can control your background exposure with the shutter speed, and then control your subject exposure from the flash with the aperture. Think of it like this. Have you ever watched a professional photographer, especially in a studio, use a light meter? They will fire off the studio lights while holding the meter next to their subject. Afterwards they will make an adjustment on the camera, and maybe take another quick test. What they are doing is using the light meter to tell them what the aperture setting should be for a particular light. Most times they will use two or more lights and all of them will have a slightly different aperture value setting so they can control the look of the photograph with shadows and such. by using different light intensities from each light. They set their camera based on the light coming from the Key or main light.

Once I began to understand this basic principle about using speedlights, it changed my fear of using them into an adventure where I rarely use just natural light anymore when shooting location portraits. Knowledge changes everything about photography. It opens opportunities that were not available before and gives you the photographer creative control of how you want the finished product to look.