O.B.A. -Optical Brightening Agent:

Used to brighten the paper. Absorbs UV light and re-emits in the visible spectrum giving the appearance of a whiter or bluer sheet.

OCR -Optical Character Recognition:

Special kind of scanning software which provides a means of reading printed characters on documents and converting them into digital codes that can be read into a computer as actual text rather than just a picture.

OCR Numbering:

Refers to Optical Character Readable figures as specified by banks, usually on giros etc.

Offset Lithography:

The process of using an intermediate blanket cylinder to transfer an image from the plate to the paper. See also Lithography.

Offset Paper:

Uncoated paper designed for use in offset lithography. Important properties include good internal bonding, high surface strength, dimensional stability, lack of curl, and freedom from foreign surface material.

Offset Printing:

Offset printing is a printing is a printing process that uses metal plates and ink; it is characterised by the use of a blanket cylinder, a rubber plate that picks up the image from the metal plate itself and then transfers that image onto the sheet of paper. In offset printing, the actual plate never directly touches the paper. Read more...

Offsetting:

Using an intermediate surface used to transfer ink. Also, an unpleasant happening when the images of freshly printed sheets transfer images to each other.

Ok Sheet:

Final approved colour inking sheet before production begins.

Opacity (ISO):

Measure of the percentage of light passage through a sheet of paper. The more opaque a paper is, the less show-through there will be from printing on the sheet below. Basis weight, brightness, type of fibres, fillers, coatings and formation all influence opacity. Generally, opacity and brightness are inversely related to each other: the brighter the paper, the less opaque. Other factors that affect opacity are bulk, surface smoothness and shade.

Opaque:

A printer's term meaning to paint out areas on a negative not wanted on the plate.

Optical Brighteners:

Also called fluorescent dyes, these are used extensively to make very high bright, blue-white papers. They absorb invisible ultraviolet light and convert it to visible light on the blue/violet end of the spectrum.

Original:

Any copy which is to be reproduced.

Origination:

A term used to describe all the processes which prepare a job for the printing stage.

Outline Font:

A font in which each character's shape is stored as a mathematical outline. It can be scaled to any size with no loss of quality and will print at the highest available resolution. PostScript, TrueType and GX fonts are outline-font formats. Also called a scaleable font -compare to bitmapped font.

Outline Halftone:

Removing the background of a picture or silhouetting an image in a picture.

Output Screen Ruling:

The number of lines per inch (lpi) that a job is output at. lpi is governed by the printing process.

Over-Exposure:

Where too much light has been allowed into a film resulting in poor detail and weak colours:

Overlay:

The transparent cover sheet on artwork often used for instructions.

Overprinting:

Printing over an area already printed. Used to emphasise changes or alterations.

Overrun or Overs:

Copies printed in excess of the specified quantity. Printing trade terms allow for + -10 % to represent a completed order.

"Ozalid":

The name of a company that markets diazo process products and equipment that makes diazo blueline prints used primarily in the US by engineering and architectural firms. However diazo or "Ozalid" proofs are most often used in England, other European, Hong Kong, Korean, and Singapore by printers as the proofing means comparable to our Dylux, or Blueline proof.