[zoppo]

jomaga wrote:
Think about common (measured) reflectances in real world:

White (very white) glossy paper : Reflectance 88% --> 224
White mate paint : Reflectance 81% --> 206

You should´nt rise this 224 reflectance, very few materials have higher reflectances in real world.
Oscar is right, reflectances avobe this number increase rendering time and produce results far from reality.

jomage, this is very interesting - where did you get this numbers?
i'd really like to know more about this.

thanks in advance, z.

[deneb26]

hi zoppo

the numbers are calculated like this: 255 is the max. value for a RGB-channel
now take 88% of it and you got 224.4
you may calculate the same with all other values.

greez
ale

[zoppo]

not exactly what i meant

i'd like to know where to get some spreadsheet (or sth like that) where you can find those numbers for the various materials. is there some kind of list with all the reflectances from a-sphalt zu z-orbium???

[Hugh]

Googled it, and got these in a couple of minutes:

Asphalt (black) 5% reflectance

Concrete (new) 40% reflectance (old) 25% reflectance

Red brick 25% reflectance

Grass (green) 40% reflectance

Face (Caucasian) 18% reflectance

Snow 95% reflectance.

Other than that, working as a light fixture/application designer, I can testify to the following. Its almost impossible to find a white metal finish higher than 88%. If you look at the white panels on washing machines, etc. You're looking at white with a reflectance of between 83% & 86%. For those of you that use a Maxwell plastic instead of metal. The highest reflectance of polished aluminium you can buy is 95%.

Just as a side note, when doing lighting calculations on a white painted room, you would very rarly allow for a reflectance higher than 70%.

[jomaga]

this reflectance values are measured data in the visible spectrum of some kind of materials, made by optics institute of Madrid.
I made this measurement two years ago for the architectural faculty of Madrid.

White paint reflectance: vertical: reflecrance. Horizontal: wave lenght
We have to choose a short range of wavelenght : green range (between 530 - 630 approx)



Cheers

[thomas lacroix]

Googled it, and got these in a couple of minutes...

my english isnt that good, so can i ask you what you typed in the search pad?
thanks...

[Hugh]

The exact search was "reflectance chart", but to be honest it didn't turn up anythng more useful than those in my last post. I'm going to keep looking though, as there must be an anorak out there who has compiled a comprehensive list.

[Duncan]

Good thread, learning lots about reflectance values !

Thanks

[Ric_535]

nice image also Fritz - im still trying to figure whats best - to use a skydome or physical sky for lighting interiors

Yes very interseing and useful thread so far!

i would never have thought to use less than 100% white for my walls before - Doh!

[Ric_535]

Physical sky and Sun - default

All Materials set to 81% (206) reflectance (diffuse)



Shutterspeed - 1/20
ISO - 250
fStop - 8

Burn - 0.5
Gamma - 2.2

7.5 HOURS - SL18

_____________________________________________________

Here is a re-render of the first image but with materials as above, The burn is also upped

A lot more light has to be let in than before as the materials are not reflecting as much but therefore the shadows and image itself look a lot more natural i feel!