Neutral gray optical colored glass is a type of optical filter material that exhibits uniform and flat spectral attenuation across the entire visible spectrum (400 nm ~ 700 nm). It neither selectively transmits a specific color nor selectively blocks a specific wavelength band. Instead, it provides proportional, wavelength-independent uniform absorption of incident light — much like adding an "optical gray mirror" into the optical path.
Excellent spectral uniformity
Can be used in combination for flexible attenuation
Limited transmittance precision
| Color Category | Typical Spectral Characteristics | Peak Transmission Band | Cut-off / Attenuation Band | Typical Applications |
| Blue | Blue-green bandpass, red/NIR cutoff | 400–520 nm | ≥ 550 nm (cut-off) | Underwater photography filters, fluorescence excitation, color temperature correction, laser safety windows |
| Gold | Yellow-orange bandpass, blue/UV cutoff | 530–620 nm | ≤ 480 nm (cut-off) | Sodium line filtering, night vision protection, low-light imaging, fluorescence observation |
| Green | Green bandpass, dual cutoff (red & blue) | 500–560 nm | ≤ 480 nm & ≥ 610 nm | Traffic signal filters, machine vision contrast enhancement, reticle aiming |
| Purple | Violet-blue bandpass, mid-IR & visible cutoff | 350–450 nm | ≥ 480 nm (cut-off) | UV fluorescence excitation, black light filters, currency authentication, biochemical analysis |
| Red | Red bandpass, green/blue cutoff | 620–750 nm | ≤ 590 nm (cut-off) | Laser sight filters, traffic signals, IR temperature measurement windows, darkroom lighting |
| Neutral | Uniform attenuation across full visible spectrum, no wavelength selectivity | 400–700 nm (uniform transmission) | No cut-off peak; constant transmission | Light intensity adjustment/attenuation, laser power attenuation, exposure control, optical balancing |
