Screen Printing from a Photo: Making Artwork That Prints Clean

Two Ways to Print a Photograph

There are exactly two approaches, and picking the wrong one accounts for most failed prints.

Threshold (line art). Every part of the image becomes either solid ink or bare garment. The result looks like a bold poster illustration. It is forgiving of mesh count, emulsion quality and press setup, and it is what most one-colour photo prints on apparel actually are.

Halftone. Continuous tone is simulated with dots of varying size. This can reproduce a photograph convincingly, but it demands a high mesh count, good emulsion, accurate exposure and a well-set-up press. On a home setup it usually produces either a blocked screen or a muddy print.

Recommendation: unless you have a controlled exposure setup and experience with your mesh, use threshold. A bold, well-executed high-contrast print looks intentional. A failed halftone looks like a mistake, and there is no way to rescue it after the screen is burned.

Reducing a Photo to One Colour

The goal is a recognisable subject in solid black on white, with no greys anywhere.

1. Choose a photo with directional light. Threshold conversion depends entirely on the light-dark structure of the original. Flat lighting has no structure to find.
2. Crop tight and remove the background. Upload to the screen printing converter — background removal happens first, which prevents backdrop tones from merging into the subject.
3. Set the threshold for recognisability, not detail. Move it until the subject reads clearly with the fewest separate regions. Squint at the screen: if you can identify the subject while squinting, it will print.
4. Check the minimum feature size. Anything thinner than your mesh can hold will either not expose or will clog after a few pulls.
5. Clean up speckle. Isolated dots are the main cause of pinholes in the emulsion. Erase them.
6. Export as SVG or high-resolution black-and-white PNG at final print size.

The result being simpler than the photo is not a compromise — it is the design. The most durable screen printed apparel graphics are almost always high-contrast and reductive.

Mesh Count Sets Your Detail Limit

Mesh count is threads per inch, and it caps the finest detail your screen can physically hold — no artwork preparation gets under that limit.

A useful rule for halftones: LPI should be roughly one quarter of your mesh count. Pushing beyond that means the dots fall between threads and either fail to expose or fill in solid.

Higher mesh is not automatically better. A 305 mesh deposits much less ink, so a bold design on dark fabric printed through fine mesh looks weak and under-covered. Match the mesh to the design: bold graphics on 110–160, detailed work on 200+.

Preparing the Film Positive

The film positive is what blocks UV light during exposure. Its quality directly limits everything downstream.

• Opacity is everything. Black areas must be genuinely opaque. Hold the film up to a bright light — if you can see through the black, the emulsion under it will partially cure and wash out unevenly. Printing two copies and taping them in register is the standard fix for a printer that cannot lay down enough ink.
• Print at 100% scale. Any scaling changes your line widths, which you chose to match your mesh.
• Use the right film. Waterproof inkjet film for inkjet printers, laser film for laser printers. Regular transparency sheets in an inkjet produce a smeared, non-opaque mess.
• Mirror only if your process needs it. Emulsion-side-down exposure gives crisper results, and whether that requires mirroring depends on your setup. Test with text before committing.
• Keep a border. Leave at least 50 mm of clear film around the design so it can be taped down without covering the image area.

Common Failures and Their Real Causes

Fine lines washed out during development. Underexposure or lines below the mesh limit. If bold areas came out fine and only thin lines failed, it is the mesh limit. If everything is soft, it is exposure.

The screen clogged after a few pulls. Detail too fine for the mesh, or ink drying in the screen. Fine detail in a high-viscosity plastisol on a coarse mesh will always clog.

Pinholes throughout the print. Dust on the film or screen during exposure, or speckle in the artwork itself. Clean everything, and remove isolated dots from the design before exporting.

The print looks muddy and undefined. Usually a threshold set too low, so mid-tones all became solid black and merged. Raise it until features separate again.

Halftone dots filled in solid. LPI too high for the mesh, overexposure, or too much squeegee pressure. Drop to a lower LPI first — it is the most common cause by a wide margin.

Edges look ragged. Low-resolution source artwork. A raster image at 150 DPI has visibly stepped edges at print size; vector artwork does not have this problem at any size, which is the main practical reason to work in SVG.

Multi-Colour Work from a Single Photo

One-colour is where most photo-based screen printing should start, but two approaches extend it without full process colour:

Two-colour separation. Convert the photo twice at different thresholds. The first, higher threshold gives you only the darkest areas — print this in black. The second, lower threshold gives a larger region — print this first in a mid-tone. The result reads as three tones (garment, mid, black) using two screens. Registration matters, but far less than full process work.

Underbase for dark garments. Printing light ink on a dark shirt needs a white underbase: the same artwork, printed first in white, then the colour on top. Choke the underbase slightly — shrink it by roughly 0.5 mm — so any registration error shows garment rather than a white halo.

Full four-colour process from a photograph is a different discipline, requiring accurate separations, matched inks and a well-registered press. It is not a natural next step from one-colour work.