A quick background for you non-photogs: A specular highlight is just the reflection of your light source on an object. In the example below, the yellow areas indicate the specular highlights. There are two specular highlights on the 8-ball because I was using a flash on-camera to trigger the main flash that was off to the right. This makes a good point. My on-camera flash is not bright enough to contribute to the exposure of the image but the billiard ball so shiny that the light is reflected and appears in the image as a specular highlight. With a little creativity, this knowledge can come in quite handy. The white arrow points to what is known as the diffused highlight (the entire bright side of the billiard ball). As in the game of billiards, the control of specular highlights is geometry in practice.
Enough background, let's get down and dirty. Remember how I said that knowing how to manipulate specular highlights can come in handy? That is the whole point of this assignment: to use the specular highlight of a light source as an interesting background element. Typically, a traditional studio portrait uses several lights: a main light, a background light and sometimes a hair light. At weddings, I find myself trying to create studio-quality portraits 1) quickly, 2) in random rooms/hallways and 3) with a minimal amount of gear. Using specular highlights, I can create a portrait with one light. All I need is a dark reflective surface to use as a background. These can easily be found once you are looking for them. The trick is to line yourself up so that you see the reflection of your light on the background (imagine the light is the cue ball and you are the pocket or vice-versa). Placing the specular highlight somewhere near Karen's face helps draw the viewer's eye to her.
Lucky for me, Karen (my wife) is a an excellent model and very patient with me. Lately, I have been focusing on Karen's pregnant belly, but for this we just concentrated on portraits.
This is from my perspective. You can see the reflection of the umbrella in the door (it's not as pronounced here because I lowered the exposure so you could see the umbrella). The dark part of the image on the right is the inside of the closet. PS, if any of you were interested, you now know what color we painted the nursery!
That's all for now!