What is CTP in printing?

The older process went from file to film to plate: output film separations, then expose the plate through them. Every one of those steps introduced a chance for dust, misalignment and a slight loss of sharpness, and each one took time. CTP removes the middle step entirely — the laser writes the image straight onto the plate.

The result is a sharper dot, better register between separations, and far greater consistency between one plate and the next. It is also considerably faster, which matters when a job has to move from approval to press in a day.

One plate is imaged per colour. A four-colour CMYK job needs four plates; each additional spot or Pantone colour adds another. That is the mechanical reason colour count drives offset cost, and why an extra brand colour is a real line on a quote rather than a rounding difference.

The plate then works on the simple principle offset lithography is built on: the imaged areas are made ink-receptive and water-repellent, the non-image areas the reverse, and the press exploits the difference thousands of times a minute. Whether plate-making is done in-house or bought in affects turnaround, and is a fair question to ask any printer.