About CR-39 lenses

  • CR-39 is the 39th formula of a thermosetting plastic developed by the Columbia Resins project in 1940. 
  • CR39 is transparent in the visible spectrum and almost completely opaque in the invisible UV range   
  • Almost half the weight of glass  
  • Highly resistant to shattering
  • Highest abrasion and scratch resistance of any uncoated optical plastic 
  • The index refraction is only slightly lower than crown glass  
  • They have a high Abbe number which yields a low chromatic aberration 

They have a high Abbe value

Abbe value is a number that describes the lens's ability to separate white light into its full spectrum of wavelengths or component colours, i.e. think of the Pink Floyd album cover where the white beam of light is being dispersed through the pyramid prism into the rainbow of colours.  

CR-39 lenses have a high Abbe value of 59.3, making them a superior lens with the least distortion from dispersion. Low-quality lenses with a low Abbe value cause a higher dispersion of light, creating chromatic aberration. 

Their index of refraction gives them a superior ability to bend light  

When light travels from less dense air through a denser glass or plastic lens, it changes its speed which causes it to change direction and bend. This is called refraction. Refractive index, or index of refraction, measures the bending of the light through the lens. The lens's refractive index determines how much the path of light is bent or refracted.

The index refraction of a CR-39 lens is only slightly lower than crown glass giving them an amazing ability to bend light through the lens providing crystal clear vision with little distortion. 

They have low chromatic aberration 

Chromatic aberration is a distortion of the image due to the inability of a lens to focus all colours to the same point caused by its dispersion. The lenses index of refraction varies with the light's speed, affecting its ability to bend the light correctly. 

CR39's higher Abbe value means better peripheral optics with less chromatic aberration 

They absorb and reflect the entire UV spectrum

CR-39 lenses have an added special UV coating, infusing organic dyes and metal oxide pigments that absorb and reflect the entire UV spectrum, which consists of a wavelength range of 100-400 nm and is divided into three bands: UVA (315-400 nm), UVB (280-315 nm), UVC (100-280 nm).  

UV400 are the ultimate protection for your eyes

'UV400' refers to UV rays at the highest end of the UV spectrum, up to the 400-nanometre wavelength. Sunglasses with this level of protection block an even broader range than the CE and British Standard models, making them the ultimate protection for your eyes. All ENKI CR-39 lenses are UV400.    

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The Kalbelia Tribe, Rajasthan India 2015
Creative Direction Jesse Walker. Photography Sarah Christensen