How Do You Determine Brightness Of Paper?

[TechnicGeek]

Hello,

 

Is it possible to manually determine paper brightness? I have matte paper and I don't know its brightness level. I wonder if there's a way to determine it or you need special equipment?

 

Thanks.

[OCArt]

Most packages state the brightness and I believe this is determined by a densitometer. I think the best you could do at home is to visually compare the test paper to known samples. Be sure to use a variety of light sources as some papers have optical brighteners that convert UV into visible light. That's how some laundry detergents achieve "brighter whites."

[Ileach]

You need some special equipment, starting with the correct light, standard-complient illumination.

If you have the data you can do the math.

 

It is pretty easy:

 

where

• Y is the Y tristimulus value (relative luminance),
• (x,y) is the chromaticity coordinate in the CIE 1931 color space
• (x_n,y_n) is the chromaticity coordinate of the perfect diffuser (reference white)

 

For some more information have a look here. And something easy to read here.

 

And if you do not have any suitable light source, ask your friends if anyone works somewhere where they need norm light (reproduction, printing, thinks like that). Having the correct light is the first step to see color.

Edited July 12, 2016 by Ileach

[El Gordo]

Not quite I think the above is about whiteness, not brightness (http://www.papersizes.org/whiteness-brightness.htm), you would need some tools to do it correctly as well

[TechnicGeek]

Thank you. I saw this brightness is measured by ISO, lumen and candela. I am working with product catalogue management system and it asks me only for either lumen or candela. I am not sure if those are how paper whiteness/brightness is measured. More like brightness because they both have to do with illumination?

[El Gordo]

Now I am getting confused... lumen and candela are units related to the "brightness" (lumen as unit for luminous flux actually) of light sources (lamps and LEDs for instance). I am not aware of its use in paper "brightness" . The TAPPI scale for brightness of paper gives the amount of reflected light of specific wavelength under specific viewing conditions in comparison to a reference material, it does not carry units, it is a relative number. So either I missed something or the input form of your database asks for something irrelevant for "paper brightness" imo. Anyone from the paper industry reading to confirm or correct?

[dcwaites]

As El Gordo says, Lumen | Candela are units for glowing sources like light bulbs.

Paper normally gives you a 'Whiteness' measure

 

In the linky for Australian Reflex Ultra White it gives you a measurement of Whiteness of 160.

However, there is also a Fluorescence Brightness measure of 25%. Perhaps this is what you are looking for.