- John's Pro-Photo Tips -

Balancing Interior and Exterior Light

What does "balancing interior and exterior light" mean?

Balancing interior and exterior light is a common problem in amateur photography, being the under exposure of indoor subjects when the camera metering is picking up light through a window. So how do we balance a darker interior subject against a brighter exterior background?

So let's take a closer look ....

To illustrate this, I have photographed an indoor pot plant against a window into a garden on a bright sunny day. I chose a pot plant because photographing a close object against a more distant background also illustrates focus and depth of field, which is the range of distance from the camera in which the subjects will be sharp.

You can read more about this in my section on camera settings.

So let’s look closer at the issue and how we can resolve it …

The following images were all shot at ISO 400 using a tripod....

Img 1:

illustrates the classic problem of balancing interior and exterior light when a camera’s metering system detects and exposes for light from a window.

In this shot I started by focusing on the background and exposing for the exterior sunlight. This shot was taken at 1/200 sec at F/5.6. The background looks great, but the flowers are too dark and very blurred.

Img 2:

Taken at 1/50 sec at F/5.6, I have focussed on the flowers and exposed for the ambient light in the room. Now the flowers look better, but the background is washed out, being way over exposed and blurred.

Now let’s look first at the focus. A wide-angle lens and smaller aperture will provide greater depth of field, which is the range of depth of distance from the camera where the subjects will be sharp.

Img 3:

I have moved the camera slightly closer, zoomed out to a wider focal length to compensate (remember the wider angle the lens the greater the depth of focus) and stopped down the aperture as far as possible. This shot was taken at 1/4 sec at F/32.

In focussing on the pot plant, the background is not completely sharp, but much better than the previous image. However, the pot plant is now too dark.

Img 4:

I have retained depth of focus by keeping the aperture at F/32, while improving the exposure on the pot plant by increasing the shutter speed to 1 full second. Unfortunately, while this has improved the light on the pot plant, the exterior background is now over exposed.

To solve this, we must go back to the image before last…… Shooting again at 1/4 sec at F/32.

Img 5:

Finally, in Img 5, I have added flash set to a power setting to expose at F/32. In doing this, it is important to remember:

Flash is not powerful enough to overpower the sunlit background, but it can increase the light to the closer and darker foreground.

Flash exposure is only affected by the aperture or ISO setting on your camera. Shutter speed does not affect the flash on shutter speeds usually below about 1/250 sec, depending on the camera. The shutter opens, the flash fires, the shutter closes.

Three step summary to Balancing Interior and Exterior Light ....

Determine your aperture for the depth of focus you want. Choose a small aperture if you want a sharper background or a larger aperture for a blurrier background.
Then set your shutter speed to correctly expose the background for your selected aperture setting.
Finally, set your flash to expose at the correct power for your selected aperture.

YOU NOW HAVE A PICTURE BALANCING INTERIOR AND EXTERIOR LIGHT!

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