Sharpness/DOI
Sharpness refers to the clarity and definition of the edges in a reflected image. It is closely related to DOI but focuses specifically on the steepness and clarity of the edges in the reflection.
Sharpness is important for high quality, high gloss surfaces as it directly impacts the visual quality and clarity of reflected images on surfaces. This clarity is essential for maintaining high visual appeal in products such as automotive finishes, consumer electronics, polished stone, reflective metal parts and high-end furniture.
Aesthetix sharpness measurement are proven to corelate to visual perception. Test samples with varying surface qualities were measured using the Aesthetix and compared to human observers who independently rated the clarity of the reflection in the sample surfaces. Statistical analyses proved a strong correlation between the instrument's sharpness values and perceptual ratings.
Aesthetix sharpness is derived from a camera image of a light source reflected in a samples surface- the measurements are more sensitive than DOI.
Sharpness Scale
Sharpness Units | Description |
|---|---|
0-20 SU | Very low sharpness, indicating a highly blurred reflection with indistinct edges. |
21-40 SU | Low sharpness, where the reflected image is somewhat blurry but edges are more discernible. |
41-60 SU | Moderate sharpness, with clearer edges and a more distinct reflected image. |
61-80 SU | High sharpness, showing a very clear and distinct reflected image with sharp edges. |
81-100 SU | Very high sharpness, indicating an exceptionally clear reflection with extremely sharp and well-defined edges. |
Relationship Between DOI and Sharpness
While both DOI and sharpness are measures of image clarity in reflections, they focus on slightly different aspects:
DOI evaluates the overall clarity and distinctness of the entire reflected image.
Sharpness specifically assesses the clarity and definition of the edges within the reflected image.
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 this is often done by measuring the spread of light around the specular angle. 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.
DOI measurement cannot be used for non-flat surfaces.
Limitations of DOI (Distinctness of Image) to quantify orange peel.
DOI can be used to quantify orange peel effect 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.
DOI is not sensitive enough to low levels of orange peel on high-quality surfaces
For improved measurement of Orange Peel- Waviness is recommended.