Pentax K-5 Operating Manual page 145

Lens Correction
Reduces distortions and lateral chromatic aberrations occurring due to
lens properties.
• Distortion
Distortion is the phenomenon in which the center of the image appears
inflated (barrel distortion) or the center of the image appears pinched
(pincushion distortion). Distortion occurs more easily when using a
zoom lens or a small diameter lens, and straight walls or the horizon in
the image appear curved.
m m m_=lm_
____ ___1
Pincushion distortion
r'-Tm
L_.L_J
Barrel distortion
• Lateral chromatic aberration
Lateral chromatic aberration is the phenomenon in which the
magnification of the image varies according to the colors (wavelengths
of light) when a picture was taken, and may cause a blurred image.
Lateral chromatic aberration occurs more easily at shorter focal lengths.