I/O Vignetting (Optical Vignetting)
Vignetting is the reduction of an image's brightness or saturation at the periphery compared to the image center.
Types: Mechanical, Optical, Natural, Pixel. Correction: Flat-field subtraction, Lens profile calibration.
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🧒 Explain Like I'm 5
Imagine looking through a long paper towel tube. The middle is bright, but the edges are dark because the tube is blocking some of the light. That's exactly what happens inside a camera lens to cause vignetting.
🤓 Expert Deep Dive
Technically, there are four types of vignetting: 1. Mechanical: Caused by physical obstructions like lens hoods or stacked filters. 2. Optical: Caused by the length of the lens barrel shadowing peripheral rays (the 'cat's eye' effect). 3. Natural: Governed by the 'Cos4 Law of Illumination', where light fall-off is proportional to the fourth power of the cosine of the angle. 4. Pixel: Specific to digital sensors, where light hitting the edge of a pixel well at an angle is blocked by the surrounding structure. In modern digital photography, most vignetting is automatically corrected in the camera's firmware or in editing software using 'Lens Profiles'.