Seeable Lumens Vs. Lumens

The number of lumens as well as the type of lumens -- photopic or sotopic -- determines how well an object is lit.

Light affects people visually and psychologically. The intensity of the light source, and the amount of light hitting an object from a certain distance, characterize the light's brightness.

Identification

One foot candle (12.57 lumens of light) is the amount of light striking an object one foot away from the light source. As objects move away from the light, less light hits them, so if they need more light, either place the objects closer to the light source or add more lights.

Lumens

Light meters measure lumens, determining the quantity of light being produced. However, they only measure the light spectrum's yellow-green (photopic lumens) section, detectable by the cone receptors of the eye -- not the spectrum's blue portion (scotopic), which is perceived by the rods. In other words, the color of the light source affects the color of the objects it hits.

Seeable Lumens

Seeable lumens assess the light spectrum's combined photopic and scotopic regions, meaning they're visible to both the cones and rods. Light source quality affects the way people register true colors, as compared to bright sunlight, which is described by the color rendering index (CRI) and the correlated color temperature (CCT).

References

• The LED Light Company: Lumens, Illuminance, Foot-candles and Bright Shiny Beads...., by Robert H Bryant
• IWI Lighting: Choosing the Right Light Bulb
• Q Energy Solutions: Measuring Lumens, What Are Pupil Lumens?
• Ezine Articles: What Are Lumens & Candle Power? How Do I Select a Flashlight? by Mike Hanigan

Resources

• Maintenance Engineering Limited: How the Eye Sees
• Projector People: Lumen Guide
• Energy Federation Incorporated: Light Levels and Lumens