Every screen printing job starts with a digital file. What arrives in the prepress department determines — more than any other single factor — the quality of the final print. A well-prepared file shortens the prepress process, produces cleaner separations, and results in sharper, more accurate prints. A poorly prepared file costs hours of correction work, produces compromised separations, and sometimes cannot be saved at all — requiring a complete artwork rebuild from scratch.

This guide covers everything a screen printer, prepress specialist, or designer needs to know about digital file preparation for screen printing: file formats, color modes, resolution requirements, vector vs. raster artwork, and a complete troubleshooting section for the most common file problems.

The Two Fundamental Types of Digital Artwork

All digital artwork falls into one of two categories: vector or raster. Understanding the difference is the foundation of all file preparation decisions.

Vector Artwork

Vector files store artwork as mathematical descriptions of shapes — lines, curves, fills, and outlines defined by coordinates and equations. Because they are mathematical rather than pixel-based, vector images can be scaled to any size without any loss of quality. A vector logo printed at 5cm looks identical to the same logo printed at 5 metres — perfectly crisp edges at both sizes.

Vector file formats used in screen printing:

When vector is ideal:

Raster (Bitmap) Artwork

Raster files store artwork as a grid of individual pixels, each with a defined color value. The quality of a raster image is fixed at the time it is created — it cannot be enlarged without losing sharpness. Scaling a raster image up causes visible pixelation (stair-stepping on diagonal edges).

Raster file formats used in screen printing:

When raster is appropriate:

File Format Requirements by Job Type

Spot Color Jobs (1–4 Colors, Bold Graphics)

Ideal format: Adobe Illustrator (.AI) or .EPS with all elements in spot color (Pantone or custom named spot colors)

Requirements:

Why spot colors matter: If artwork arrives with RGB or CMYK fills instead of spot colors, the prepress operator must manually match and reassign every color. This takes time and introduces matching errors. Spot colors labeled “PMS 185 C” or “Custom Red” communicate exactly which ink to use.

Photographic / Process Color Jobs

Ideal format: Adobe Photoshop (.PSD) or .TIFF, RGB color mode, 200–300 DPI at print size

Requirements:

Mixed Artwork (Photo + Text + Graphics)

Many real-world designs combine photographic elements with vector text and graphic elements. The correct approach:

  1. Create the vector elements in Illustrator at correct scale
  2. Place the photographic elements as linked or embedded raster images at 200–300 DPI
  3. Either: deliver as a layered .PDF that preserves both vector and raster elements, or flatten to a high-resolution .TIFF for raster-only workflow

Color Mode: The Most Critical File Setting

Color mode determines how colors are stored and interpreted in a digital file. Using the wrong color mode is one of the most common — and most consequential — errors in screen printing file preparation.

RGB (Red, Green, Blue)

RGB is the native color mode of screens, cameras, and scanners. It is the correct working mode for photographic artwork intended for halftone or index color separation.

Use RGB when:

CMYK (Cyan, Magenta, Yellow, Black)

CMYK is the color mode of offset printing. In screen printing, CMYK is relevant only when outputting a standard four-color process separation.

Common mistake: Designers convert artwork to CMYK “because it’s for printing.” In screen printing, converting photographic artwork to CMYK before separation compresses the color gamut and introduces conversion artifacts that reduce the quality of the final separation. Keep photographic artwork in RGB until the separation stage.

Spot Color (in Illustrator/vector files)

Spot colors in vector files are not a color “mode” in the same sense — they are named color swatches assigned to objects. Each spot color will become one screen in production.

Use spot colors when:

Indexed Color

Indexed color mode in Photoshop is the output of index color separation — not an input format. Never deliver artwork to a prepress department in Indexed color mode; it cannot be correctly edited. If you have an indexed color file that needs modification, convert back to RGB first (Image → Mode → RGB Color).

Grayscale

Grayscale is the correct mode for individual separation channels and single-color photographic prints.

Resolution: Getting It Right

Resolution is the most frequently misunderstood specification in screen printing file preparation. There are three common errors:

Error 1: Screen Resolution Files (72 DPI)

Files downloaded from websites or captured in screenshots are typically 72 DPI — the standard screen display resolution. A 72 DPI image at 10cm × 10cm contains only 204 × 204 pixels. At 300 DPI for print, that same physical size requires 1181 × 1181 pixels. The 72 DPI file has 97% fewer pixels than needed.

What happens: Halftone dots become irregular and chunky. Index color pixels become large and blocky. Fine detail is simply absent.

Fix: Request the original high-resolution file. If unavailable, discuss with the client whether the artwork can be recreated in vector format.

Error 2: Upsampled Files

Some clients (or designers) increase the DPI of a low-resolution file in Photoshop by changing the resolution field without unchecking “Resample.” This creates a file that reports 300 DPI but contains only the original pixel information — artificially inflated. The file looks larger in file size but contains no additional detail.

How to identify upsampled files: Open in Photoshop and check pixel dimensions. A genuine 300 DPI file at 30cm × 30cm should be approximately 3543 × 3543 pixels. If the pixel dimensions are much lower despite reporting 300 DPI, the file has been upsampled.

Fix: Same as above — request the original file.

Error 3: Correct DPI But Wrong Physical Size

A 300 DPI file at 5cm × 5cm is not suitable for a 30cm × 30cm print — even though it is technically “300 DPI.” Resolution must be specified at the final print size.

Always check: Image → Image Size in Photoshop. Confirm both the pixel dimensions AND the physical size at the intended DPI.

Preparing Vector Artwork: Common Issues and Fixes

Fonts Not Converted to Outlines

When a file is opened on a system that doesn’t have the same fonts installed, text will substitute to a default font — changing the appearance of the design completely. Converting text to outlines (paths) eliminates font dependency.

Fix: In Illustrator: Select All → Type → Create Outlines. Check that no text objects remain in the Layers panel.

Strokes Set as Appearance (Not Expanded)

A 2mm stroke in Illustrator is a display property applied to a path. If the file is scaled or placed in another application, the stroke weight may behave unexpectedly. Expanding strokes converts them to filled shapes with defined dimensions.

Fix: Select All → Object → Expand Appearance. Then Object → Expand (check both Fill and Stroke).

Overlapping Objects with Transparency

Transparent or semi-transparent objects in vector artwork create complex color interactions that may not separate correctly. Particularly problematic: multiply blend mode, opacity below 100%, and gradient transparency effects.

Fix: Flatten transparency before delivering files. Object → Flatten Transparency. Check “Convert All Strokes to Outlines” and “Convert All Text to Outlines” in the dialog.

RGB Colors in a Spot Color Job

If a spot color job arrives with RGB fills (even if the colors “look right” on screen), the prepress operator must manually match and reassign every color. This introduces matching errors and adds time.

Fix: In Illustrator, open the Swatches panel. Create named spot color swatches for each intended ink color. Select all objects of each color and assign the correct spot color swatch.

Linked Images Not Embedded

Illustrator files can contain linked images — references to external files — rather than embedded image data. If the linked file is not included with the delivery, the placed image will not display or output correctly.

Fix: File → Package (bundles all linked files with the document) or: Links panel → select all links → Embed Image(s).

Preparing Raster Artwork: Common Issues and Fixes

JPEG Compression Artifacts

JPEG compression discards image data to reduce file size. At low quality settings, this produces visible block patterns and edge ringing that appear in the separation and print as irregular dots and blurry edges.

Fix: Always work from uncompressed originals (PSD or TIFF). If only a JPEG is available, inspect carefully at 100% zoom for compression artifacts. A high-quality JPEG (90%+ quality) is acceptable; low-quality JPEGs are not suitable for halftone work.

Wrong Color Profile or Missing Profile

Color profiles define how numeric color values in a file translate to actual colors. A file with a missing or incorrect color profile will display differently on different systems — what the designer saw as a warm orange may appear as a cool red in prepress.

Fix: Embed a standard color profile in all delivered files. For photographic work: sRGB IEC61966-2.1 is the most widely compatible choice. In Photoshop: Edit → Assign Profile → sRGB.

Merged vs. Layered Files

A merged (flattened) file is appropriate for final delivery to prepress. A layered PSD is appropriate when the prepress department will be building separations from the layers.

Clarify with your prepress provider whether they prefer flattened or layered files. Dragonfly Colors works with both — but a clearly organized layered file can accelerate the separation process for complex designs.

File Delivery: What to Include

When delivering files to a screen printing prepress department, include:

For vector spot color jobs:

For photographic / process color jobs:

Troubleshooting: Common Digital File Problems

Problem 1: File Arrives at Incorrect Size / Resolution

Symptoms: File is too small for print size; pixelation visible at intended print scale.

Causes and fixes:

Problem 2: Colors Shift When File Is Opened

Symptoms: File looks correct in designer’s delivery email but wrong when opened in prepress software.

Causes and fixes:

Problem 3: Text Appears in Wrong Font / Layout Broken

Symptoms: File opens with font substitution warning; text appears in incorrect typeface; layout has shifted.

Causes and fixes:

Problem 4: Transparency Effects Not Printing Correctly

Symptoms: Drop shadows, glows, or gradient transparency effects appear differently in print output than in the design file.

Causes and fixes:

Problem 5: File Contains Too Many Colors for Available Screens

Symptoms: Design has 15 different colors but job is budgeted for 6 screens.

Causes and fixes:

Common Mistakes with Digital Files for Screen Printing

1. Delivering a logo grabbed from a website. Website graphics are 72 DPI and often heavily compressed. They cannot be used for screen printing without rebuilding. Always request the original vector file from the client.

2. Converting artwork to CMYK before delivery. For photographic work, this pre-compresses the color gamut and reduces separation quality. Keep photographic files in RGB.

3. Not converting text to outlines. One missing font installation can ruin a prepress workflow. Convert all text to outlines as the final step before delivery — always.

4. Sending a PDF without checking the content. PDFs can contain low-resolution images embedded within a vector wrapper. A PDF that looks sharp on screen can contain 72 DPI raster elements. Open in Acrobat and check image resolution via Tools → Print Production → Output Preview.

5. Not specifying print size. “Send me the file for the print” with no dimensions specified means the prepress department must guess. Always specify exact print width × height in centimetres or inches.

6. Using the wrong color names for spot colors. “Red” is not a color specification. “PMS 185 C” or “Pantone 485 C” or a precise CMYK/Lab value is. Vague color names require a matching conversation that should have happened before the file was created.

7. Delivering a layered file without a flattened reference. A layered PSD with 20 layers is only useful if the prepress operator knows which combination of layers represents the final intended appearance. Always include a flattened reference image showing the correct final look.

Summary: Screen Printing File Preparation Checklist

Vector spot color files:

Raster photographic files:

A well-prepared file is a professional courtesy to everyone involved in the production chain — and a direct investment in print quality. The five minutes spent checking a file before delivery saves hours of prepress correction work and eliminates the most common cause of disappointing print results.

Dragonfly Colors accepts all standard file formats for color separation. If you’re unsure whether your file is correctly prepared, send it to us for a free prepress check. Contact us before starting your project.