Lens Aberrations

Chromatic Aberrations.
 - Light passes through glass elements and is dispersed into it's correct colours.
 - Axial and Traverse - Common in wide angle lenses. 


Axial Aberrations
 - Can be reduced by careful use of the other aberrations


Types of Aberrations
 - Achromatic
 - Aporchromatic
 - Superchromatic 


Coma (NOT COOMA)
 - An off axis sperical aberration creating cone shaped points.
 - Stopping down can slightly reduce effects.


A Stigmatism
 -  Axis aberration causing vertical and horizontal lines to be focused in two different planes.
Image Distortion 
- Pin cushioning and lens barrelling
- Image sharpness not affected 
- Cannot be reduced by stopping down