# 45° Sparkle Measurement

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The Effect Finish module quantifies how visible and intense sparkle effects appear when an effect coating is viewed at a 45/0 geometry, i.e. illuminated at 45° and observed close to the normal. At this angle, sparkle is often more pronounced and directional, so these parameters are particularly useful for matching appearance in real-world viewing conditions on automotive and other effect-coated parts.  

## SpR (45°), SpG (45°), SpB (45°)  
- SpR (45°): Sparkle Red 45° is the red-channel intensity of sparkle elements seen at 45°, indicating how strong the red component of the sparkle appears at this off‑specular angle.  
- SpG (45°): Sparkle Green 45° is the green-channel intensity of sparkle elements seen at 45°, describing the green contribution to the sparkle impression.  
- SpB (45°): Sparkle Blue 45° is the blue-channel intensity of sparkle elements seen at 45°, describing the blue component of the sparkle effect.  

## Density (45°)  
- Density (45°): Sparkle Density 45° is the number of visible sparkle points per 100 mm² at 45°, describing how densely the surface appears filled with sparkle elements when viewed from this angle.  
- Higher Density (45°) values indicate a busier, more active sparkle field, whereas lower values correspond to a sparser, more subtle effect.  

## Area (45°)  
- Area (45°): Sparkle Area 45° is the average size of detected sparkle elements at 45°, representing the typical image area covered by individual sparkles.  
- Larger Area (45°) values suggest coarser, more prominent sparkle particles, while smaller values correspond to fine, pin‑point sparkle.  

## Brightness (45°)  
- Brightness (45°): Sparkle Brightness 45° is the average luminance of the sparkle points at 45°.  
- Higher Brightness (45°) values mean that individual sparkle points are more intense.  

## Visibility (45°)  
- Visibility (45°): Sparkle Visibility 45° is the average perceived brightness of sparkle elements at 45°, taking into account their visibility and the background colour of the material.  
- This parameter is designed to correlate with human perception of how noticeable the sparkle effect is at 45°, combining contributions from density, area and brightness against the underlying coating colour.




| Parameter group      | Parameter         | Unit             | Description                                                                                                                        |
|----------------------|-------------------|------------------|------------------------------------------------------------------------------------------------------------------------------------|
| 45° sparkle metrics  | SpR (45°)         | Intensity (0–255)| Red‑channel sparkle intensity at 45°, indicating how strong the red component of the sparkle appears at this off‑specular angle. [3] |
|                      | SpG (45°)         | Intensity (0–255)| Green‑channel sparkle intensity at 45°, describing the green contribution to the sparkle impression. [3]                     |
|                      | SpB (45°)         | Intensity (0–255)| Blue‑channel sparkle intensity at 45°, describing the blue component of the sparkle effect. [3]                              |
|                      | Density (45°)     | 1/100 mm²        | Number of visible sparkle points per 100 mm² at 45°, describing how densely the surface appears filled with sparkle elements. [3] |
|                      | Area (45°)        | mm²              | Average size of detected sparkle elements at 45°, representing the typical image area covered by individual sparkles. [3]   |
|                      | Brightness (45°)  | AU*              | Average luminance of the sparkle points at 45°, indicating how bright each sparkle appears relative to the surrounding surface. [3] |
|                      | Visibility (45°)  | AU*              | Average perceived brightness of sparkle elements at 45°, taking into account their visibility and the background colour of the material. [3] |

\*AU = arbitrary (instrument) units.