# Question about fresnel IOR

**URL:** <https://forums.chaos.com/t/question-about-fresnel-ior/53011>\
**Category:** General\
**Tags:** fresnel, ior\
**Created:** [March 11, 2015, 3:15pm UTC](https://forums.chaos.com/t/question-about-fresnel-ior/53011 "2015-03-11T15:15:08Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![fooprobe](https://avatars.discourse-cdn.com/v4/letter/f/43a26b/32.png) [@fooprobe](https://forums.chaos.com/u/fooprobe)\
**Post date:** [March 12, 2015, 6:22pm UTC](https://forums.chaos.com/t/question-about-fresnel-ior/53011/5 "2015-03-12T18:22:31Z")

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the “fresnel IOR” is just the refractive index of the material as used in the fresnel equations, _n_ in the wikipedia entry. Metals are uniformly reflective, they do not exhibit fresnel reflections (the wikipedia entry on fresnel reflections notes an exception for conductive materials in general). That said, I have always been confused by the reflections IOR option in the standard material fresnel map. maybe it lets you have a different IOR for light transmission (“refraction”) and for reflection - which again doesn’t exist in the real world.

vray lets you do all kinds of things that don’t exist in the physical world. like having a different “highlight glossiness” and “reflection glossiness”. Maybe someday some materials scientist will invent a material that does have really high IOR.

So increasing the “fresnel IOR” beyond numbers that actual materials actually exhibit just plugs that number into fresnel’s equations, and it approximates a metal and you get a more uniform reflection.

if you want a more fresnel-like effect on a metallic reflection (that is, very reflective), try using the falloff map in the reflection color map, or use an angle-blend material with a more-reflective and less-reflective material.

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