Here’s a quick and dirty lesson by accomplished DP, Julia Swain on how to use a light meter and why it can improve your lighting game if you don’t use one already. If you have a scene your filming with a specific camera setting in mind, like f-stop, a light meter can help you measure your lighting setup and make adjustments if necessary to achieve the look you want.
Your camera has 4 different settings that affect exposure:
Most of the time you’d want to set your camera to it’s native ISO and then the preferred f-stop, followed by frame rate and shutter speed. Now, input those setting into your light meter. A light meter can tell you how many stops over or under your lighting is within your scene. The light meter used for our demonstration is made by Sekonic, but nearly all light meters operate the same way and typically can take two types of readings. One type is incident reading, which measures how much light is falling on a subject and suggest what a normal exposure would be based on those settings.
This doesn’t mean set your camera to those settings, but it will help you to establish lighting ratios of each light on your subject so you can make a determination how you’d like to use your lighting. The other light reading is spot reading, which measure reflective light, from sidewalks, TVs and walls just to name a few. Light absorbs and reflects through out a space so this reading is great to help you put a number on the amount of light being reflected into your lens.
Next we have Ted’s on-set demonstration where he’s showing how to use a light meter to get specific lighting ratios for different moods or looks. Settings input to the light meter are: 24fps/ 400 ISO, so he’s gonna get an incident reading of the key & fill light falling on his subject separately. Below are images of lighting ratios of key light vs fill light. Below are examples of different lighting ratios suitable different styles, like sitcom or drama. The ratios are based on footcandle readings (FC), so a 4:1 ratio (160fc:40fc) is great for TV show comedy and 16:1 (160fc:10fc) is common for more dramatic productions.
Lighting used in this episode: 2x Aputure 120d and 2x Aputure Light Domes