How to Balance Ambient Lighting with Flash

One of the biggest challenges faced by photographers when shooting outdoors is when the background is at a different level of illumination from the subject in the foreground. This happens mainly in backlit situations, such as when you are photographing a model at the golden hour. The background is brilliantly lit with all different hues and the subject, unless she is standing facing the light, is silhouetted; giving you a nightmare of a situation to correctly expose for.

Does this sound all too familiar? So how do you overcome a situation like this and get away with an image that has both the background and the subject properly exposed? If you use the auto-exposure mode of your camera, it will do what it is meant to do, take a reading of the whole scene and try to make an average, so that everything is properly exposed. Even though 3D metering systems used in modern digital cameras have a come a long way since the early days of digital photography, they are still not a replacement for what the human eye can see or do.

Do you then manually try to meter? The problem here is if you expose for the background, the subject will be too dark, and if you meter for the subject, the background will be blown out. What you need is an additional light source, preferably an off-camera one, which will allow you to balance the exposure in this situation.

You would still be metering manually, but now with some assistance. The first question is how do you ensure that you have the right exposure for both the subject and the background? They are after all lit differently. This is where a light meter can be very helpful. Check out our tutorial on How to Use a Light Meter. A light meter can be used to read both incident and reflected light, which is what you need in order to meter the whole scene perfectly and set your flash power. We talked about the flash in the previous paragraph, now you know why we need it. We need it to illuminate the subject.

First, hold the meter to read the ambient light of the background. Let’s say at ISO 100 and aperture f/8 it gives a shutter speed of 1/60 of a second for the background. Now, the next step is to adjust the power of your flash / strobe so that the exposure on the subject is balanced. Take another reading to check the flash exposure. At its default power setting it could be higher than what the background metering was. If it’s higher than the background you will need to cut down the power so that the meter reads f/8. Now the exposure for the subject and the background are both balanced. Not a lot of people use light meters these days and if you don’t have the budget for one you can technically just hone the setting in by trail and error with test shots. However a light meter would make this task much easier and faster (which is very useful during sunset scenes).


Overpowering strobes make the sky look dramatic in this rooftop image.

In case you want the background to be slightly underexposed, so that it appears less dominant, there is one more thing that you could do. Use a slightly faster shutter speed, narrower aperture and bump up the power of your strobe. The faster shutter speed will ensure that the background is darker than the foreground. But remember that your camera and flash have a limited sync speed (around 160/250 of a second), anything above that would require a hyper sync (aka high speed sync), unless your are using a leaf shutter lens (but you would know it if you do). When flashes are in hyper sync they are significantly less powerful and need to be positioned much closer to the subject. If you are not ready to delve into hyper sync just yet, keep the shutter speed below 160 of a second.

The above techniques can be used indoors as well, especially when you have a mixed lighting situation – flash plus ambient light.

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This entry was posted by Rajib Mukherjee.

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