Colour, inks and printing

The colour you asked for is the colour that comes off the press — and the printing works takes the file without asking questions.

A colour on a screen and a colour on paper are not the same thing. A screen mixes light; a press lays down ink. A document that says no more than blue leaves the answer to whichever machine prints it, and the answer changes from one machine to the next.

A document made here can say exactly what it means: the inks a press will really lay down, a brand colour ordered by name and run on a plate of its own, and a plain statement of the printing condition the file was prepared for. A printing works reads that statement and knows what it is holding.

What it saves you

Your brand colour is the same on every document
A colour ordered by name is run from its own plate, so it is reproduced rather than approximated by mixing others — which is why two batches of the same leaflet can come back different.
The printing works accepts the file
The document carries what an operator would otherwise have to telephone and ask for. A job that comes back is not merely late: the sheets already run are waste and the press is idle.
The same numbers mean the same colour everywhere
The file states what its numbers stand for, so the colour does not drift between the screen it was approved on and the press it is printed on.

See it done

Every one of these is a real PDF this library wrote, with the source that wrote it.

Grey, screen and printing colours

Swatches in each of the three ways to say a colour — a grey as one number, a screen colour as three, a printing colour as four inks — each captioned with the instruction actually written into the file, and one mid-grey said three ways.

Colour the document defines

The same six colours said as bare numbers and then read through the sRGB profile the file carries, plus a ramp from light to dark and a sweep of hues in CIE L*a*b*: colour that still means the same thing on another screen and on a press.

Inks on plates of their own

Two inks the press carries on a plate of their own, each at ten strengths, a piece of work set in both, and the crosses used to line the plates up — drawn in an ink every plate answers to.

Several plates at once, each at a strength of its own

Eight choices of plate among the four usual inks, each with the small program that shows it printed underneath, and two inks the press carries itself used together, every strength of one against every strength of the other.

A chart of colours, and a drawing that names places in it

A chart of house colours the file carries, and a drawing whose sixteen numbers are places in that chart rather than colours. The same drawing is shown twice through two charts: repainting a whole brand is one table, not every drawing.

One hatch, laid down in as many colours as the page asks for

One pattern that states no colour of its own, laid down in five colours and in five strengths of one press ink: the fill says what colour to lay it down in. Beside them, the same hatch made of patterns that carry their own colours, which is one pattern per colour.

A sheet as it goes to the press

One drawing on three pages: a press sheet stating where the ink runs, where the blade falls and what is worth keeping, with corner marks; the same sheet cropped to the finished page; and a landscape page that states a quarter turn clockwise on an upright sheet.

A sheet a printing works runs without asking a question

One sheet larger than the finished page: the colour runs nine points past the blade, the corner marks stand outside it in an ink every plate carries, every colour is said in the four printing inks, and the page names the paper, the edge of the ink and the cut. Hand it the profile of a press and it claims PDF/X-4; without one it claims nothing, and says on the page why.

The same numbers, through spaces that say what they mean

Six colours and a grey ramp painted three times over with the very same numbers: first left to the device, then said in two ways that state the white they are measured against, the curve applied to them, and how far the base colours reach. All of that travels in a handful of numbers, with no profile to carry.

The device a file's colours are meant for

The output intent a file carries, printed on the page it describes: the printing conditions, their description and the profile behind them, with a ramp and one swatch per ink painted through that same profile. Hand a press profile on the command line and the page is drawn in that press's inks instead.

Functions, the shape a colour follows

What a function says a colour does, in each of its four kinds: a spectrum read off a table of values, a ramp cut into bands by a small calculation, an ink whose conversion recipe is a program printed under its swatches, and a table joined end to end between two ends.