Understanding Exposure: Light Chapter

I bought Bryan Peterson's book 'Understanding Exposure' years ago when I first got into digital photography. It was helpful at the time to improve my understanding of the exposure triangle (aperture, shutter speed and ISO). There is a chapter in the book devoted to the subject of light, and I thought this would be a good starting point for my research in this part of the course. I made brief notes on useful information in this chapter, starting with an interesting quote:

The light is the best frosting for the cake, but it isn't the cake.

In other words, the lighting in an image is an extremely important feature of an already creatively correct image; light enhances the photo which you have already planned with a creative exposure.

Exposures in the midday sunlight are harsh and contrasty without any real warmth. The best natural light is in the early-morning and late-afternoon; both reveal textures, shadows, and depth in warm and vivid tones. This light combined with a change of weather such as an incoming storm or rain shower is also great.

The colour of light varies: early morning light is golden, but cooler than the stronger golden-orange light an hour before sunset. Weather, especially inclement weather, can change the colour of light.

Light is considered as coming from three directions:

low-angled front light provides even illumination

side light provides a three dimensional effect

strong back light provides silhouettes

Front Light

The quality and colour of front light is best in the first hour after sunrise, and during the last few hours of daylight. Frontlight evenly illuminates, making for a straightforward exposure.

Overcast front light also illuminates evenly. The light is very soft, good for natural looking portraits, and richer colour flowers. Also eliminates contrasts problems that occur on a sunny day. A very suitable light for auto-exposure modes; aperture or shutter priority can easily be used depending on the creative requirements.

Side Light 

Front-lit subjects often appear two-dimensional, even though your eyes tell you the subject has depth. Highlights and shadows produce an illusion of three-dimensionality, and this can be achieved with side light. For several hours after sunrise and several hours before sunset you will get side light if you shoot towards the north or south. You should consider underexposing by one stop to further darken the shadows. Side-lit subjects elicit a much stronger response from viewers than front-lit or back-lit because it better simulates the three-dimensional world they see with their own eyes.

Back Light

With back-lighting it is easy to make silhouettes. Exposing for the whole scene will render a silhouette; if you want to properly expose for the subject, then fill the frame with subject then exposure lock before backing away and recomposing the image.

Back-lighting offers a variety of exposure options:

1) Meter for the strong back light to create a silhouette.
2) Meter for the light falling on the subject, excluding the back light - good for portraits.
3) Meter for the light that's illuminating a somewhat transparent subject, such as leaves and dew-covered spider webs. Semi-transparent subjects don't silhouette in back light - they appear to glow.

Like many exposure options, successful back-lit scenes result from a conscious and deliberate metering decision.