# Distinctness of Image DOI

## Distinctness of Image
Distinctness of Image (DOI) refers to the measure of how clearly and distinctly an image is reflected off a surface.

The ASTM definition of DOI, or Distinctness of Image, refers to a measure of the sharpness and clarity of a reflected image on a surface. 

This is particularly used in contexts like automotive finishes, where the visual quality of a surface is critical. 

DOI quantifies the extent to which a surface can reflect an undistorted image. A higher DOI value indicates a clearer, more distinct reflection, whereas a lower DOI value indicates a more blurred reflection caused by surface irregularities like orange peel texture.

DOI measurement was specified in the 1950's using fixed sensor which measured the spread of light at fixed angles. 

A narrow spread indicates a sharp image, while a wider spread indicates a blurred image.

The physical limitation of sensor placement reduces the sensitivity of this measurement for very high quantity surfaces, sharpness measurement adjusts according to the reflectance profile of the surface. Sharpeness is 

DOI measurement cannot be used for non-flat surfaces.

| DOI   % | Description                                                                                                    |
|---------|----------------------------------------------------------------------------------------------------------------|
| 0-35    | Very low sharpness, indicating a highly blurred reflection with indistinct edges.                              |
| 35-60   | Low sharpness, where the reflected image is somewhat blurry but edges are more discernible.                    |
| 60-85   | Moderate sharpness, with clearer edges and a more distinct reflected image.                                    |
| 85-85   | High sharpness, showing a very clear and distinct reflected image with sharp edges.                            |
| 95-100  | Very high sharpness, indicating an exceptionally clear reflection with extremely sharp and well-defined edges. |

## Limitations of DOI (Distinctness of Image) -quantifying orange peel. ##
DOI has often be used to indirectly quantify orange peel on paint surfaces. 
However, it has the disadvantage that other surface effects, such as surface micro-texture, can reduce DOI independently of the presence of orange peel.

For improved measurement of Orange Peel- Waviness is recommended.

