The DOI (Distinctness of Image) Difference for Floors

How flooring DOI can improve customer perception of facilities

by Donald Landin — We’ve heard it many times: One of the first things people notice upon entering a facility is the floor, and if those floors aren’t shiny and clean, it reflects poorly on the facility. In addition to potential health risks, dirty floors can give visitors a negative image of a business or facility’s overall operations while clean, well maintained floors create a positive first impression. One way building owners and operators can improve customer perception of their facilities is to ensure their floors have a high distinctness of image (DOI).

What is DOI?

DOI is best defined as the measure of how crisply and sharply an image is reflected from a surface, indicating the clarity of a reflection seen in the floor. DOI is gaining popularity and quickly becoming the new measure of floor restoration, protection, and maintenance quality. It should not be confused with other measures like gloss, haze, and RSpec measurement.

Gloss. The most popular term used to describe the appearance of a floor’s surface is gloss. Gloss refers to shine or light reflection and causes surfaces to have a polished or lustrous, metallic appearance. Many factors can affect gloss, including the maintenance materials used, condition of the flooring, and frequency of polishing. For customers, gloss has been one of the most important aspects of visual perception.

To measure a floor’s gloss, a meter projects a beam of light onto the floor and measures the amount of light reflected back in a narrow angle range centered at an equal but opposite angle. The amount of light measured in this angle range is used to calculate gloss. However, the clarity of a reflected image is dependent on the spread of light within the measured angle range. If light is predominantly at the center of the range, the image will be crisp and clear. Light spread more evenly across the entire angle range will result in a blurry image. Thus, the amount of reflected light measured on two different floors might be the same but have a much different distribution across the measurement. So two floors with an equal gloss could have very different appearances.

This is why traditional gloss measurements alone don’t always equate to a favorable customer perception.

Haze. This is the milky halo or “bloom” on a floor adjacent to the reflected image. If you place a high light source on a surface and the reflection image blooms and creates a blurry halo, the surface is considered high haze. Haze is an important measure for highly polished surfaces. Higher haze values indicate lower quality and can be caused by dirt or oil contamination creating a rough surface. If the surface or coating is not completely smooth, the reflection of light or image is scattered, broadening the specular gloss.

Floor maintenance professionals strive for a low haze value, which is seen to have a deep reflection and high-reflected contrast. Hence, haze is a common measurement of maintenance quality. Yet while haze affects the clarity and reflection of surfaces, it is only one aspect of surface quality and doesn’t measure the overall floor’s appearance.

Did You Know?

  • 70 percent-80 percent of all the dust, dirt, and grime in public buildings comes from outside.
  • In 20 working days 1,000 people will track about 24 pounds of dirt through a building entrance.
  • A 15-foot floor mat will trap almost 85 percent of the dirt tracked into a building.
  • Floor care accounts for almost 40 percent of a custodian’s time.

Source: ISSA, IEHA

RSpec. Peak specular reflectance (RSpec) is the peak gloss value of a surface. It is the gloss measured only at the specular angle and is the peak gloss reading. Specular gloss is the reflection of an object on a perfectly smooth surface, such as a mirror, in which the reflection is sharp and clear. Of course, if a surface is not perfectly smooth, it scatters the reflection of the light beam and broadens specular gloss.

RSpec is limited in measuring the true appearance of a surface because it only represents the peak gloss value. It does not take into account the distribution of light around the specular angle.

DOI takes this distribution into account, and therefore is an accurate measure of the clarity of the reflected image.

How to Measure DOI

If the surface reflection of an object appears sharp and clear, such as being able to see the clear outline of an overhead light bulb or read the text in a reflected sign, then the surface is said to have a high DOI. Conversely, if the reflection appears blurry, then it has a low DOI. The DOI measurement is similar to gloss measurement, but with minor changes. It accounts for the distribution of the reflected light collected across the angular measurement range.

The American Society for Testing and Materials (ASTM) has set standards for test methods determining the DOI of coating surfaces. Measurements are given on a scale of zero to 100, with a score of 100 representing perfect DOI. For more information on these standards, see ASTM D5767-95.

How to Achieve High DOI

DOI is directly affected by the condition of a floor. One can use top-of-the-line products, but if the floor is covered with scratches and dings from lack of proper maintenance, it will not reflect an image to its best ability. This may lead to haze, orange peel (a wavy pattern of light and dark areas on a high gloss surface), or a blurry image. The solution includes following a regular floor maintenance routine to keep the floor in top shape.

When choosing a maintenance system, the products included are very important. Achieving high DOI doesn’t need to be difficult. Generally speaking, most protection and polishing products aim to produce only a glossy appearance, but that goal is quickly changing. Today, there are increasing numbers of specially engineered floor maintenance systems that include products, such as abrasives, finishes, and burnishing pads, designed specifically to increase DOI.

Many companies now recognize the priority of having DOI-friendly products that work with the rest of the maintenance system to not only enhance a floor’s gloss, but to dramatically increase DOI as well.

With facility guests and occupants taking greater note than ever of a building’s cleanliness—and often basing their judgment on appearance—it is imperative for floors to be well-maintained and have a lustrous finish. Stay on the forefront of the growing DOI trend by protecting your floors and enhancing your image. Your customers will notice.

A National Floor Safety Institute certified walkway safety auditor, Don Landin, Ph.D., is senior technical service specialist for the Hard Floor Care Lab in the 3M Building and Commercial Services Division. He can be reached at or visit

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