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Why do cameras use multiple lens elements instead of one lens?
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Cameras use multiple lens elements instead of a single lens to correct for aberrationsāinnate imperfections that prevent a lens from focusing light into a perfect point. A single lens typically produces a blurred image with defects such as colour fringes or distorted lines.12
By combining several lens elements of different shapes, materials, and separations, designers can ensure that the aberrations produced by one element are counteracted by the opposite aberrations of another. These compound lens systems are essential for achieving acceptable image sharpness. Specific corrections include:12
- Chromatic aberration: Corrected by combining lenses of different refractive properties to bring different colours of light to a common focus.13
- Spherical aberration: Addressed by using multiple elements or aspheric surfaces to ensure light rays passing through the rim and center of the lens converge at the same point.42
- Other defects: Complex arrangements also mitigate issues like astigmatism, coma, curvature of field, and distortion.5
The complexity of these systems increases with the desired aperture size, angle of coverage, and level of precision required.2