Retina

The internal lining on the back of the eye that contains light sensitive rod and cone receptors and a network of nerve cells.

L. Stroebel and R. Zakia

Original

The term original refers to the negative (positive if reversal processed) or image file from a digital camera that was in camera when the object was photographed.  It also applies to sound recordings on film, or video recordings.  Original are also materials from which copies are made, such as handwritten, typed or computer generated documents, printed material, tracings, drawings, etc.  The term can also apply to original work/s of art.

I. Current (Updated by R. M. Elliott)

Diffuser

Any light-scattering medium placed in the path of a beam of light so as to soften the character of the light.

S. Ray

See also: Diffusion

Neutral

• Colour name given to pure achromatic colours, that is, whites, greys, and blacks that are not tinged with any hue.
• Colour name given to pure achromatic colour stimuli, that is, stimuli whose chromaticity coordinates are the same as those of the illuminant.

R. W. G. Hunt

See also: Achromatic

Achromatic

• Term applied to a lens corrected for longitudinal chromatic aberration to bring light rays of two colours (wavelengths) in the visible spectrum to the same focus.
• Term used in physics to describe colours that have no hue or saturation and only lightness. White, grey, and black are examples of achromatic colours.

S. Ray

See also: Neutral