Angle of Reflection = Angle of Incidence


To get a correct reflection in your subject, you need to know how to position your reflector to direct the light from your original light source.

Topics Covered:

  • Utilizing Light Sources and Reflectors

Equipment Used:

Lighting Equipment

  • Photoflex LiteDisc
  • Photoflex LiteDisc Holder
  • Photoflex Starlite Kit Medium

Figure 1

The physical law of light states that "the angle of reflection is equal to the angle of incidence". The angle of incidence is the angle that light is striking a surface. The angle of reflection is the angle that the light is reflected, or bounced (figure 1).
To simply illustrate this seemingly complicated law, we begin this reflector demonstration by positioning a 32" x 42" softbox and light at 90 degrees to the right of the subject. This will be our "main" light (figure 2).
We set the ice bucket in the middle of the main light area (figure 3).


Figure 2


Figure 3


Figure 4

We are using this highly reflective ice bucket so that you can easily see how the light and reflections look. We don't necessarily think that this is how you should light this product if you were trying to take a photo of it, we are using it to show you how this lighting concept works.
As you can see from the results, the main will give you a nice even highlight that wraps around the ice bucket and gradually tapers off (figure 4).

To give the left side of the ice bucket some more detail in the shadow area, we positioned a white 42" LiteDisc on the left side. The photo term for this is a " bounce fill".
We set-up the bounce fill 90 degrees to the left of the subject in a similiar position as the "main" light. So, if the reflection is equal to the angle of incidence, then light aimed directly at a reflector will bounce directly back (figures 5 and 6).
Or for you techie people, if the incident of light is 90 degrees, than the angle of reflection will be 90 degrees.


Figure 5


Figure 6


Figure 7

As you can see, the reflection on the left is a mirror image of the highlight on the right (figure 7).

Here is our first illustration with the "main" only and the second photo with the "main" and "bounce fill" for comparison (figures 8 and 9).


Figure 8


Figure 9

To further demonstrate this basic principle, we set the "main" at approximately 45 degrees to the ice bucket, and positioned it farther away (figures 10 and 11). We kept the subject in the middle of our light spread area.


Figure 10


Figure 11


Figure 12

Here is the results photo. You can see that the highlight is moved more to the front of the ice bucket. The highlight is smaller because we moved the main light farther away from the subject (figure 12).

Our next step is to add our bounce fill. We set the white 42- inch reflector on the LiteDisc holder to left of our subject at about a 45 degree angle (figures 13 and 14).


Figure 13


Figure 14


Figure 15

In our results, we see the effect of the bounce fill on the subject. We now have soft, open light with both of our light sources coming from the front of the subject (figure 15).

In figure 16, we see the comparison of all the final images. You can easily see the results of each of our steps.


Figure 16


Related Lessons

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Light Control and Macro Photography
Learn how to soften sunlight when shooting closeup shots in your garden.
Senior Portraits using Litediscs Outside
Strategic placement of reflectors can enliven outdoor portraits.
Creating Cinematic Lighting the Easy Way
LitePanel reflectors and existing light can offer great results outdoors.
Controlling Reflections in Impossibly Reflective Objects
Reflective objects can be very difficult to shoot, but you can learn some effective methods for getting great results.

Lighting Equipment

  • Photoflex LiteDisc
  • Photoflex LiteDisc Holder
  • Photoflex Starlite Kit Medium

Continue reading here: Understanding How Soft Boxes Work: Part

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Readers' Questions

  • julie
    How does the angle of incidence compare with the angle of reflection?
    1 year ago
  • The angle of incidence is equal to the angle of reflection. This is known as the Law of Reflection.
    • frediano
      Is the angle of incidence equal to the angle of reflection?
      1 year ago
    • Yes, the angle of incidence is equal to the angle of reflection.