O – Glossary of Print and Design Terms
Welcome to our comprehensive glossary of print and design terms. We are continually seeking to grow and improve this glossary, so if you spot any definition you do not agree with, a term that is missing, or have any comments in general, please email our reference team.
| OCR | Optical Character Recognition. An application which can recognise scanned printed type and convert it into editable text on a computer |
| Offset | The most commonly used printing method, whereby the printed material does not receive the ink directly from the printing plate but from an intermediary cylinder called a blanket that receives the ink from the plate and transfers it to the paper |
| Offset Gravure | A complex offset process involving multiple transfers between the gravure plate, the plate cylinder and a solid rubber plate |
| Offset Paper | Paper which is uncoated or coated and strong enough to resist the pull of tacky inks used in offset lithography |
| Offset Printing | A lithographic method of printing in which the ink is first transferred from the image to an offset blanket and then to the stock |
| OKTP | Generic abbreviation for OK To Print. An indication of approval for press |
| On Demand | Usually refers to printing output only when it is needed instead of having it stored on the shelf |
| Onionskin | A light bond paper used for typing and used with carbon paper because of its thinness. |
| Opacity | 1. Characteristic of paper or other substrate that prevents printing on one side from showing through the other side. 2. Characteristic of ink that prevents the substrate from showing through |
| Opaque | A quality of paper that allows relatively little light to pass through |
| Opaque Ink | Ink that completely covers any ink under itself |
| Open Format | A file format which can be used royalty free. The TIFF file format in its uncompressed state can be used freely while the LZW compression function is used under licence |
| Open Prepress Interface (OPI) | Hardware and software that link desktop publishing systems with colour electronic prepress systems |
| Operating System | An operating system is the core program that manages all other resources and applications on a computer. Examples of operating systems include Microsoft Windows, UNIX, Apple MacOS |
| Optical Density | This is the range of tones that can be captured by a device. Optical density is measured on a scale of 0 for white to 4, which is black |
| Optical Resolution | Maximum spatial resolution without recourse to interpolation. Resolution imaged by optical system in a capture device – without subsequent software interpolated pixels |
| Origination | The preparatory stages for printing a book. It can include typesetting, redrawing artwork, making halftones and colour reproduction of photographs |
| Orphan | First line of a longer paragraph that prints as the last line of text on the page |
| Orthochromatic | Any light sensitive surfaces that are not sensitive to red |
| Outer Forme | Forme (side of a press sheet) containing images for the first and last pages of the folded signature (its outside pages) as compared to inner forme |
| Outline Halftone | Halftone in which background has been removed or replaced to isolate or silhouette the main image. Also called knockout halftone and silhouette halftone |
| Overhang Cover | A cover of a book that extends over the trimmed signatures it contains |
| Overlay | Layer of material taped to a mechanical, photo or proof. Acetate overlays are used to separate colours by having some type or art on them instead of on the mounting board. Tissue overlays are used to carry instructions about the underlying copy and to protect the base art |
| Overlay Proof | Colour proof consisting of polyester sheets laid on top of each other with their image in register, as compared to integral proof. Each sheet represents the image to be printed in one colour. Also called celluloid proof and layered proof |
| Overprint | To print one image over a previously printed image, such as printing type over a screen tint. Also called surprint |
| Overrun | Quantities of sheets printed over the requested number of copies |
| Overs | Non-waste copies which, at the end of a production run, are additional to the quantity required |
| Overset | Type that is set in excess of the allotted space |
