Photopic vision operates at luminances above roughly 5 cd/m squared, where the cone cells of the retina do the seeing and give full color vision and fine acuity. Its spectral sensitivity is the V-lambda curve peaking at 555 nm, on which all standard photometry is based. Interior lighting and most of daytime life fall in the photopic range.
Photometric reports assume photopic vision, which is fine inside the shop but tells you less about the yard at night.
Also heard as
- photopic vision
- cone vision
- daylight vision
Related terms
Scotopic
Describes night vision at very low light levels, when only rod cells respond and color disappears.
Mesopic
Describes the in-between vision of twilight and street lighting, when rods and cones both contribute.
V-lambda curve
The standard curve of the eye's daytime sensitivity to each wavelength, peaking in green at 555 nm.
Luminance
The brightness of a surface or source as seen from a particular direction, measured in candelas per square meter.