I spent some time today running a set of experiments for lighting.  Before I dive into describing them, here’s a few terms for those who haven’t spent much time on photographic or cinematographic lighting.

  • The key light is the primary light used to light a scene.  Having the key at different angles to the subject has different effects on the resulting image.
  • Fill light is light that is applied to brighten up the shadows left by the key light.
  • The fill light is always dimmer than the key light (if it were brighter, it would be the key light), but the ratio of key and fill light can vary to cause different effects.

I had two goals in my experiments:

1. Determine the impact of having the key light at various angles to the subject.
2. Experiment with different key-fill ratios.

To do this, I set up my lighting like this:


In the course of doing the experiment, I varied the key angle from 30° to 90° in 15° increments.  I tested each setup with no fill light and with various key-fill ratios from 10:1 to 1:1.  I used myself as subject, with assistance from Julie.

First, let’s look at the effects of the different angles. Each of these are with no fill:






The effect is clear: the lighting gets more dramatic as the angle increases, with one side of my face disappearing when the angle hits 90°.

Note, though, that the result of specific angles depends on the shape of the subject’s face.  These angles apply to my rather round flat face – you’d need to vary them when shooting someone else.

Next, let’s take a look at the impact of the fill ratios.  For this, I’ll use the 45° key angle:









As you can see, just a little fill light can have a big impact.  But varying the key-fill ratio produces different results, with a dimmer fill causing a more dramatic look.  Note that this is one of the major aspects of film noir: dim, often non-existent, fill.

And because it will help me to have all of these in one place, here’s the entire collection – all angles, all ratios:

key-44 key-43 key-42 key-41 key-40 key-39 key-38 key-37 key-36

key-35 key-34 key-33 key-32 key-31 key-30 key-29 key-28 key-27

key-26 key-25 key-24 key-23 key-22 key-21 key-20 key-19 key-18

key-8 key-7 key-6 key-5 key-3 key-4 key-2 key-1

key-17 key-16 key-15 key-14 key-13 key-12 key-11 key-10 key-9