Print-Ready Artwork: File Preparation, Colour Management and DPI That Actually Works

Roughly a third of the artwork that reaches our pre-press desk needs work before it can go to a press. Almost none of it is because the design is bad. It is because a file that looks perfect on a laptop screen carries no information about how large it will print, what colour it must be, or what happens where it meets a black garment.

This guide covers what we need, why we need it, and how to prepare it in the software you already have. Get this right and you save a proofing round, which in practice saves three to five days.

Why files get rejected

The five reasons, in order of frequency:

1. Insufficient resolution at print size. The file is fine at 5 cm and unusable at 30 cm.
2. Raster where vector is needed. Screen printing and vinyl cutting require clean paths, not pixels.
3. Colour supplied only as RGB screenshots, with no Pantone reference and no idea which of six possible blues is intended.
4. Missing fonts. The file references a typeface we do not have, and text reflows to something else on open.
5. Hidden transparency effects — drop shadows, glows, multiply blends — that do not survive separation.

Vector vs raster, decided properly

Vector artwork is stored as mathematical paths. It can be scaled to any size with no loss. Formats: AI, EPS, PDF (vector-preserving), SVG, CDR.

Raster artwork is a grid of pixels with a fixed resolution. Enlarging it invents nothing. Formats: PNG, JPG, TIFF, PSD.

One point that catches people out: exporting a PNG from Illustrator does not make it vector. It rasterises it at whatever resolution you chose in the export dialog. If your design started as vector, send the vector source as well as the export.

DPI at real print size

DPI only means something in relation to a physical dimension. A 3,000 px wide image is 300 DPI at 25.4 cm and 100 DPI at 76 cm. The calculation:

required pixels = print width in inches × 300

Below 150 DPI at final size, edges visibly soften and text picks up a halo. Between 150 and 300 DPI, results depend on artwork type — a soft photographic image survives lower resolution than crisp geometric line work.

Colour: RGB, CMYK and Pantone

Your screen emits light and mixes colour additively in RGB. Ink absorbs light and mixes subtractively. Some RGB colours — bright oranges, vivid greens, most neons — simply have no CMYK equivalent. They will print duller, and no amount of adjustment changes that.

What to supply

• Pantone references for any colour that must match: brand colours, sponsor colours, institutional colours. Use TCX or TPG codes for fabric and Solid Coated for ink.
• A physical reference where possible — a previously printed garment, a printed brand guideline page. Screens vary; physical samples do not.
• Named swatches in the file, so separations come out labelled rather than guessed.

What each method can hit

• Screen printing — ink mixed to the Pantone reference. Closest matching available, including neon, metallic and reflective.
• Sublimation — profiled to the fabric; very good matching within the polyester gamut.
• DTF and DTG — CMYK plus white. Good on most corporate colours, unable to reach neon or metallic. We will tell you before you order if your brand colour is out of gamut.
• Vinyl — a fixed catalogue of film colours. We match to the nearest available and show you the swatch first.

Underbase and dark garments

Ink is not opaque enough to show over a dark fabric on its own. So on any dark garment, digital and screen processes print a white underbase first, then the colours on top. That has three consequences worth designing around:

• Colours shift. The same file on white cotton and on black cotton produces slightly different results, because the underbase is never perfectly neutral white.
• Hand-feel increases. A full underbase plus colour is two ink layers. On DTG it is the main reason dark prints feel heavier.
• Fine detail closes up. Very thin lines and small text can lose definition where the underbase spreads under them. Keep line weights above about 0.75 pt and text above 6 pt.

If you want the garment colour to show through part of the design, say so explicitly. “Knock out the fabric colour here” is a design decision, not something we should be guessing.

Transparency, blending and other traps

• Drop shadows and outer glows render as soft gradients. In screen printing they become halftone dots, which on a textured knit can look grainy. Consider whether the shadow is doing real work.
• Multiply and overlay blend modes depend on what is beneath them. On a garment, what is beneath them is fabric, not white. Flatten intentionally, or expect a surprise.
• Semi-transparent fills cannot be reproduced in screen or vinyl at all — those processes are binary. Convert them to solid tints or halftones yourself so you control the result.
• Anti-aliased edges on raster art produce faint semi-transparent pixels. On DTF these can leave a visible film halo. Supply clean, hard-edged transparency for cut-through designs.
• White backgrounds hiding in PNGs. A JPEG has no transparency; a PNG exported from a file with a white artboard will print a white rectangle. Check on a dark background before sending.

Preparing screen separations

If you are supplying separated artwork for screen printing:

1. One colour per layer, named with the Pantone reference.
2. All spot colours defined as spot, not process. A “Pantone” swatch converted to CMYK will separate into four films.
3. Text converted to outlines.
4. Trapping — a slight overlap between adjacent colours — of around 0.25 mm, so tiny registration variance does not show fabric between them.
5. A separate underbase layer if you want control over it; otherwise we generate one and show it to you.
6. Registration marks outside the print area.

If any of that is unfamiliar, send the layered artwork and let us separate it. Separation done badly is worse than not done at all, and we do not charge extra to do it properly.

Artwork for embroidery is a different job

Embroidery does not print your file. A digitiser converts the design into a stitch file — deciding stitch type, direction, density, sequence and underlay. That process has its own constraints:

• Minimum sizes. Lettering below about 5 mm cap height will not read. Fine detail below 1 mm disappears into the fabric.
• Colour count. Each colour is a thread change. Fifteen colours is possible; it is also slow and expensive.
• Gradients do not exist. They must be reinterpreted as blended stitch fills, which is an artistic decision — approve the digitiser's proposal rather than assuming.
• Fabric changes everything. The same file on pique, fleece and a cap needs different densities and underlay. That is why we sew a stitch-out on your actual fabric before bulk.

Placement and sizing conventions

Specify placement from a fixed anatomical point, not from the garment edge — garment edges move between sizes.

Decide early whether the graphic scales with size or stays fixed. A 30 cm print looks bold on XS and modest on 3XL. Most brands keep one size across S–XL and step it once for 2XL and above. Either is fine; specifying nothing is not.

The pre-press checklist we run

Every incoming file goes through this. Run it yourself and your job moves straight to production.

• Vector source supplied where the method requires it
• Raster art at 300 DPI at final print dimensions
• All text converted to outlines
• Fonts supplied or embedded if text remains live
• Spot colours named with Pantone references
• Colour mode appropriate to method
• Transparency and blend modes flattened intentionally
• No hidden white background behind a transparent design
• Line weights above 0.75 pt, text above 6 pt for underbased prints
• Artwork at 100% of intended print size, in millimetres
• Placement specified from the high point of shoulder
• Separations layered and labelled, or explicitly left to us
• File named with brand, garment, placement and version

Get your file checked before you order

Send artwork to our pre-press team and we will run the checklist above and tell you exactly what needs changing — before you commit to a quantity or a method. There is no charge for it, because a file checked in advance saves us more time than it costs.

Once the file is right, the printing methods guide will help you choose the process, and the quote calculator will price it.