Len Abberations
There has three main reasons to course the lens aberrations:
1. The refractive index of glass varies with wavelength are called chromatic effects.
2. Lens surfaces are generally spherical in shape are called spherical effects.
3. Light behaves as if it were a wave motion are called diffraction effects.
Generally, the effects of aberrations increase with aperture and angle of field.
There have seven errors which will cause aberrations in a photographic lens. Two errors affect all parts of the image field including the centre are called Axial chromatic aberration and spherical aberration. Another five errors affect only rays passing obliquely through the lens and do not affect the centre of the image. The effects of these oblique errors increase with the distance from the lens axis. They are lateral chromatic aberration, coma, curvature of field, astigmatism and distortion. These effects appear as the angle of field increase. Axial and lateral chromatic aberration are chromatic effects. The rest of five errors are called spherical effects.
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