Proper use of lighting ratios add shape and dimension to the subject’s face. Ratios compare the placement of the main light to the fill light, and are represented by numbers such as 1:1, 2:1, 3:1, etc. The lights cause a light and dark side of the subject. The main light illuminates the light side of a subject. The fill light creates the shadow, or the darker side, of a subject.
Lighting ratios describe the difference in contrast between the lighted side of a subject and the shadow side. The higher the ratio, the more contrast between the highlights and shadows.
Manipulating the lighting ratio when taking studio photos, or using portable lighting equipment, will help make sure your subject is well-lighted with appropriate contrast and the image conveys the intended message and mood. Follow these recommendations when determining the best lighting ratio for your photo.
- 1:1 Ratio - has flat contrast, and is often used for photographing subjects that are meant to look flawless.
- 2:1 Ratio - adds dimension, but is soft in the shadows. This is often used for photographing children and babies to preserve the feeling of innocence and purity.
- 3:1 Ratio - is optimal for black and white photography.
- 4:1 Ratio - is best used for taking official portraits.
- 8:1 Ratio - adds a dramatic effect to the subject.
To create the desired lighting ratio effect, use one of these methods:
- F/Stop Distance Scale Method
- Power Setting/Flash Meter Method
F/Stop Distance Scale Method
This method uses the distance of light placement to create the ratios. The farther away a light is moved from the subject, the less intense it will be. Distances are measured in feet, and correspond to the camera's f/stops: 2, 2.8, 4, 5.6, 8, 11, 16 and 22.
For this technique to work, all the lights in your setup must have the same output intensity. To create a particular ratio, use the difference in light intensity for a specific ratio to determine the distances to place the main and fill lights. Place the main light in one spot and move the fill light to create the desired lighting ratio. When measuring for lighting ratios, it’s important to remember that the f/stops are directly correlated to the distances for light placement, and not the setting of your camera, for proper exposure.
As an example, if you decide to shoot with a 5.6 f/stop and you need to create a 3:1 lighting ratio, then you know the main light needs be 1.5 f/stops brighter than the fill light. Using the f/stop distance scale, place the main light 5.6 feet away, and the fill light 9.5 feet away from the subject, because 1.5 f/stops greater than 5.6 is 9.5, since 9.5 is halfway between 9 and 10. Because the f/stops correspond to feet, the result is 5.6 feet and 9.5 feet to create a 3:1 lighting ratio.
In another example, if you use the same 5.6 f/stop as above, but you need to create a 2:1 lighting ratio, then you only move the fill light to create a different ratio. For a 2:1 lighting ratio, the main light needs to be 1 f/stop brighter than the fill light. Using the f/stop distance scale, place the fill light 8 feet away from the subject. You use 5.6 feet and 8 feet to create a 2:1 lighting ratio.
Power Setting/Flash Meter Method
Most studio flashes have adjustable power settings. By adjusting the output power on the flash power pack, you can create the desired lighting ratio without changing the placement of the main and fill lights. This method uses a flash meter or the camera's built in light meter setting to calculate exposure by measuring the light coming from each of the flash units individually. A flash meter tells you what exposure to set the camera for a given light intensity.
Using a flash meter is the most accurate way to calculate the lighting ratio and exposure at the same time. To achieve the proper exposure and desired lighting ratio when metering:
- Start with the main light because it determines the exposure for the entire scene. Turn off all the other lights and take a test shot of the main light’s intensity with a flash meter.
- Make adjustments to the output power of the main light and take another test shot. Continue this process of adjusting the output and measuring with the meter until you get the desired output power for the exposure you need.
- Once the main light is adjusted properly, turn it off. Move on to the other lights in your setup.