# Black Light Wavelengths: 365nm vs 395nm vs 254nm Spectrum Guide

> Author: Black Light Encyclopedia Research Group
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## Comparative Analysis
A 365 nm black light produces true UV-A radiation with virtually zero visible light, delivering maximum fluorescence contrast with no purple wash. A 395 nm light sits on the boundary of visible violet, casting an intense purple glare (15–30% visible bleed) that obscures faint organic stains and minerals.

For professional inspection (forensics, pet urine detection, art restoration, mineralogy, NDT), a 365 nm LED equipped with a black ZWB2 filter is essential. 395 nm lights are cheaper and primarily suited for scorpion hunting, fluorescent party decor, and curing UV resin.

## ZWB2 / Hoya U-340 Filter Physics
InGaN 365nm LEDs naturally produce a secondary visible emission tail (400–450 nm) due to semiconductor bandgap imperfections. Because human eyes are orders of magnitude more sensitive to 420 nm than 365 nm, unfiltered LEDs wash out faint fluorescence.
A ZWB2 bandpass filter transmits >80% of UV-A between 320–385 nm while blocking visible light (400–680 nm), outputting a pitch-black beam that only excites target fluorophores.

## Wavelength Matrix Summary
- 185 nm (VUV): 6.70 eV. Generates ozone via oxygen photolysis.
- 254 nm (UV-C): 4.88 eV. Mineralogy (willemite, calcite), germicidal sterilization (UVGI), DNA transillumination. Severe ocular hazard.
- 302 nm (UV-B): 4.11 eV. DNA gel electrophoresis, specialized minerals (esperite).
- 365 nm (UV-A): 3.40 eV. True black light. Forensics, pet urine, banknotes, art authentication, NDT (ASTM E1417), dermatology.
- 385 nm (UV-A): 3.22 eV. Industrial UV curing, optical adhesives.
- 395 nm (Near-UV): 3.14 eV. Scorpion hunting, uranium glass, fluorescent posters, craft resin.
- 405 nm (Violet): 3.06 eV. SLA 3D printing resin curing, dental composites.