We have all heard the saying “soft wrap around light”. What they are referring to is light from one source illuminating two surfaces of an object. So the light from your main light illuminating the fill light side of your subject as well. This is however a bit of a misnomer.

Light does not wrap. I know that this sounds counter intuitive to what you have been taught or what you have heard, but it is true. Light can only travel in a straight line. So, what causes this “wrapping” that everyone references? It comes from the size of the light source and the distance it is from the subject. Sound familiar? It’s the same two things that control the softness of the light.

The larger your light source is in relationship to your subject, the more light will miss it’s “intended” target. If you have a small light source and a large subject there would not be any light to pass the subject, illuminating the other side. The closer your light source is to your subject the tighter the angle of light is that leaves the modifier. The farther it is from your subject the larger the cone of light will be. Thus, the larger the area the light covers will be.

Example 1

CLARIFICATION: (Example 1)You will notice that the spread of light from each box is outlined in black. The red portions of the light spread indicate the light from our soft box that is not hitting our subject. The red area is larger for our larger box, meaning more of the light is "missing" our subject. If both of these lights are the same power the exposure will be less on the larger box since there is less light on "our intended target". (Example 2) The closer the light source is to your subject the larger it will be. See below how as we move the light source away from our subject the "smaller" it gets?

Example 2

There you have it. The truth behind “wrapping” light. I have heard many photographers theorizing about how best to make their light wrap and even more referencing the shape of the subject in terms of how the light wraps; it has nothing to do with wrapping light.

Take this information and file it away. I will continue to use the phrase “wrap around light” since this is how the photography community describes this characteristic of light. Even though it may not be “scientifically  correct” it certainly does describe it well.

If you have any questions regarding this blog, please feel free to contact Westcott Technical Rep John Williamson. He can be reached at 419.243.7311 or by email: john@fjwestcott.com.

Be sure to tune in next week for "Reflectors - The Physics behind them"