Elcometer Distinctiveness of Image (DOI)

Elcometer 408 Triple Angle Gloss & DOI Meter

Gloss & DOI Meter Definitions

Gloss (GU)

A simple measurement proportional to the amount of light reflected from a surface determining how shiny a surface appears.

Surface texture can reduce appearance quality, without affecting gloss. These two test panels have identical readings when measured with a standard glossmeter.

Haze (HU) & Log Haze (HULog)

High quality gloss surfaces have a clear, deep, brilliant finish. Haze causes a drop in reflected contrast and causes halos to appear around light sources, these unwanted effects dramatically reduce visual quality.

Undetectable by traditional gloss meters the Elcometer 408 measures Haze Units in accordance with ASTM E430 at the same time as simultaneously measuring gloss and DOI.

Peak Reflectance (Rspec)

Rspec is the peak reflectance measured over a very narrow angle in the specular direction and is very sensitive to any surface texture, waviness or rippling. When Rspec is equal to the gloss the surface is smooth. Rspec drops as the surface texture increases.

Distinctness of Image (DOI)

Distinctness of Image measures the sharpness of a reflected image in a coating surface. Similar coatings may have identical gloss values but visually the quality may be very different. A visually poor coating may have a highly textured dimpled appearance known as "orange peel". When a reflected object is viewed in such a coating the image becomes fuzzy and distorted.

A surface that has a perfect undisorted images returns a value of 100. As the value decreases the image becomes more distorted.

Reflected Image Quality (RIQ)

Reflected Image Quality provides greater sensitivity when evaluating highly reflective coatings and the specular / diffuse element of lower gloss materials.
A surface that exhibits a perfect undistorted image returns a value of 100, as the values decrease higher surface texture is present and the image sharpness reduced.


Goniophotometric Profile

The gloss, haze, DOI and Rspec values produced by the Elcometer 408 can be used to assess the visual quality of any surface. The full range of goniophotometric curves can be downloaded to a computer for detailed understanding of specular reflectance. The Elcometer 408 can also be used to quantify an orange peel finish or a substandard coating with a low DOI.