What is Spherical Aberration
Spherical aberration is a distortion of the image that results in a loss of sharpness. When the light rays passing through the edges of the lens do not converge on the same plane as the rays passing through the center, there is a spherical aberration. In this case, it is impossible to get a sharp image on the edges and in the center.
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The blur effects and halos caused by spherical aberrations are also called “diffuse light”. Spherical aberration affects the entire image area, from the center to the edges. It produces a soft image, low contrast, which seems to be covered with a thin veil.
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Aberration can be largely eliminated by reducing the opening of the diaphragm to limit the amount of stray light.
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Below a spherical lens and above a spherical mirror. The rays away from the optical axis converge at a different distance than those near it. This effect was concealed with the paraxial approach, as it was understood that all rays were close to the axis.[youtube https://www.youtube.com/watch?v=nulYyEjYTN8]
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How to cure Spherical Aberration?
The diaphragm can be used to reduce the point of the passage of light rays and for this reason, it is advisable to use a small opening. But one of the simplest techniques to avoid this diffuse light is to use a sun visor when shooting. For SLR users, it is advisable to use lenses composed in part of aspheric lenses to compensate for defects.
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It is also possible to use special type ED glasses that reduce aberrations.
Spherical aberration can be corrected in different ways:
- Using a diaphragm that prevents the passage of rays farther from the optical axis
- Combining lenses with opposite effects
Using parabolic surfaces instead of spherical
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