How to Use Guide
This guide explains the meaning and purpose of each input field in the Lighting Ratio Calculator.
Key Light Calculation Section
Target F-stop (Key Light):
Meaning: This is the aperture value (F-stop) you want for your subject's focus. It affects the depth of field (background blur) and serves as the baseline brightness for the entire scene.
Purpose: Sets the target for calculating how bright your key light needs to be to achieve proper exposure at this F-stop.
ISO:
Meaning: The camera's sensitivity to light. Higher numbers allow shooting in darker conditions but may increase noise.
Purpose: Calculates the required light intensity based on your camera's ISO setting.
ND Filter (stops):
Meaning: A filter that reduces the amount of light entering the lens. Used in bright conditions to use a wider aperture (for more blur), etc. The value indicates how many stops of light are reduced.
Purpose: If using an ND filter, this accounts for its effect when calculating necessary light intensity. A stronger light source is needed to compensate for the filter's reduction.
Shutter Setting:
If setting by Speed:
Shutter Speed:
- Meaning: The duration the shutter is open. For video, a value close to double the frame rate's denominator (e.g., 1/48s or 1/50s for 24fps) is typically chosen for natural motion blur.
- Purpose: Calculates the light intensity needed for proper exposure at this shutter duration.
If setting by Angle:
Shutter Angle (degrees):
- Meaning: The shutter's opening angle, used in cinema cameras. 180 degrees is standard, equivalent to a shutter speed of "double the frame rate's denominator."
- Purpose: Calculates shutter duration from the set angle and frame rate to determine the required light intensity.
Frame Rate (fps):
- Meaning: The number of frames captured per second.
- Purpose: Used with shutter angle to calculate the actual shutter duration.
Key Light Distance:
Meaning: The distance from the key light (main light source) to the subject.
Purpose: The intensity of light reaching the subject changes with distance (Inverse Square Law). This calculates the required brightness of the light source (intensity at 1m) to achieve the target F-stop at this distance. Select the unit (m or ft).
Fill Light Calculation Section
Lighting Ratio (Key : Fill):
Meaning: The ratio of the fill light's brightness (auxiliary light, light that fills in shadows) relative to the key light's brightness.
Purpose: For example, "2:1" means the fill light is half as bright as the key light (-1 stop), and "4:1" means it's a quarter as bright (-2 stops), adjusting the shadow density (contrast). This ratio is used to calculate the required fill light intensity.
Fill Light Distance:
Meaning: The distance from the fill light to the subject.
Purpose: Calculates the required brightness of the fill light (intensity at 1m) based on the set lighting ratio and distance. Select the unit (m or ft).
Background Light Calculation Section
Lighting Basis:
Meaning: Choose whether to base the background light's brightness on the key light or the fill light.
Purpose: The calculation source for the background light's relative brightness changes depending on which light is chosen as the basis.
Lighting Ratio (Basis : Background):
Meaning: The ratio of the background light's brightness relative to the selected basis light's brightness.
Purpose: For example, "1:1" means the same brightness as the basis, and "0.5:1" means half the brightness of the basis (-1 stop), adjusting the subject's edge emphasis or background brightness.
Background Light Distance:
Meaning: The distance from the background light to the subject (or the background area to be illuminated).
Purpose: Calculates the required brightness of the background light (intensity at 1m) based on the set lighting ratio and distance. Select the unit (m or ft).