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.
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.
Aberration can be largely eliminated by reducing the opening of the diaphragm to limit the amount of stray light.
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.
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.
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