File Preflight and Preparation: The First Gate to Print Output
Every print job begins long before the first sheet reaches a press. It begins with a file, and most files arrive built for a screen rather than for ink. Designers work toward what looks right on a monitor, and nothing in that work accounts for plates, colour separations or paper. That is why a careful shop puts a checking step at the front of the prepress workflow, before a RIP, a digital proof, a plate or a film is made. The goal is simple: catch the problems that cause output errors while they are still a few clicks away from being fixed.
What preflight is for
Preflight is the systematic review of a customer file against the requirements of the chosen printing process. It sits between design and output, and it looks at the file as a production data set rather than as artwork. A page that reads well on screen can still contain an image in the wrong colour space, a font that will not embed, or a bleed that is too narrow for the trim. Each of those faults is cheap to correct at the desk and costly to correct after plates are burned. A clean, standardised electronic file also protects the steps that follow, from raster image processing to digital proofing and plate output.
How the check is made
The everyday method is to open the file in the program that made it and inspect it with that program's own tools, correcting anything the inspection turns up. For files of unknown origin, or for a second opinion, dedicated preflight tools such as FlightCheck can examine the document and report the faults they find. Some shops run both, using the automated report to catch what the eye misses.
What gets inspected
A preflight pass normally covers page size, bleed, text, image format, image links, colour mode, fonts, effects, overprint and trapping. In practice the checks fall into four groups.
Images. Confirm that nothing is hidden, cropped away or shown with an unexpected display. Check that placed files are in a supported format and are not compressed in a way the output device cannot read. Look for RGB images in a process that expects CMYK, verify that every link points to the correct original, and confirm the resolution and physical size of EPS and TIFF files. Note any image that has been rotated, scaled, cropped or given heavy effects, because each transformation can change how the file separates.
Fonts. Confirm that type has been converted to outlines where required and that no font is missing. Look for garbled characters and for text that has shifted. PostScript fonts need both the screen font and the printer font supplied. Check that the arrangement of the text matches the design.
Colour. Remove RGB fills from jobs that will print in four-colour process, decide which spot colours are genuine and which should be converted, and delete colours that are defined but never used. Confirm that any gradient will reproduce as intended. Where overprint is used, make sure it is deliberate.
Geometry and marks. Confirm the finished size matches the job ticket, that the bleed reaches the required depth, that line weights are heavy enough to hold, and that overprint is set as intended.
Software traps worth knowing
Certain programs hide recurring hazards. In Photoshop, flatten the layers that matter and delete the channels that do not, so the saved file carries only useful data. In Illustrator, 100 per cent black is knocked out rather than overprinted unless you set it in the black overprint options, vector output should be set high enough to keep curves smooth, and white fills need their overprint flag checked or they can disappear. Illustrator also crops output to the content on the page, so a page holding a single small image will output at that small size unless a page-sized, colourless border is added or the output settings are corrected in the separation setup.
CorelDRAW has its own list. Paragraph text that contains special characters can break, small type is best kept to one or two inks, and converted type should stay under a reasonable node count. Outlining some fonts produces hollow letters. Text pasted from a word processor should have its double-byte spaces removed. Imported PSD files with transparency should be converted to a bitmap and left unrotated or unmirrored afterwards. Gradients that run from a colour to black must be defined so the black end does not punch a hole in the other plates, and spot colours cannot be given transparency or shadows without being converted.
FreeHand users should avoid placing greyscale images, outline text in mixed-language blocks, define overprints before placing files into other programs, and skip the heavy font option. In PageMaker, set image size and resolution in a proper image editor before placing, avoid scaling large images inside the layout, store long thin images as DCS, and avoid the built-in type effects that can double or drop on output.
The payoff
Preflight is quiet work that rarely gets credit when it goes well. It is also the cheapest insurance a print shop can buy. A file checked at the desk reaches the plate clean, proofs predictably, and prints the way the designer saw it on screen. When the goal is a job that looks the same at every stage, from the first soft proof to the finished sheet, the checking step is where that consistency is won.