The short answer
- Digital removes the colour-count limit and makes resolution at print size the binding constraint
- Aim for 300dpi at the finished size, not at whatever size the file happens to be
- A clean alpha channel matters more than file format
- On dark garments the white underbase is generated from your artwork — soft edges show
- Thin lines and small text fail differently in DTG than in screen printing
Artwork rules for screen printing are well understood in most shops: keep the colour count down, supply vector, watch the halftones. Digital printing changes the constraints rather than removing them, and files that were perfectly good for screen can produce disappointing DTG or DTF output for reasons nobody flagged.
The colour limit disappears — a forty-colour photograph costs the same as a two-colour logo. What replaces it is a set of quieter requirements that are easy to miss because nothing refuses the file.
What actually changes from screen printing?
| Screen | DTG / DTF | |
|---|---|---|
| Colour count | Costs a screen each | Free |
| Gradients | Need halftones or separation | Print directly |
| Resolution | Vector preferred, forgiving | Binding constraint |
| Fine detail | Limited by mesh | Limited by ink spread on fabric |
| Transparency | Handled in separation | Must be clean in the file |
| Dark garments | Underbase printed as a layer | Underbase generated from the art |
The last row is the one that catches shops out most often, and it gets its own section below. The rest come down to a single principle: in digital printing the file is the output, so whatever is wrong in the file is wrong on the garment.
Resolution at size, not resolution
The most common artwork failure in digital printing, and it is a misunderstanding rather than carelessness. A file described as 300dpi tells you nothing on its own — dpi is only meaningful against a physical size.
A 1,200 pixel wide image is 300dpi at four inches and 75dpi at sixteen. Printed at four inches it is crisp; printed as a full front it is soft and pixelated. Same file, same number, completely different result.
| Print width | Pixels needed at 300dpi |
|---|---|
| 4in — left chest | 1,200 |
| 10in — standard chest | 3,000 |
| 12in — full front | 3,600 |
| 14in — full back | 4,200 |
This is exactly why artwork checks belong on the order rather than on the file, where the intended print size is known. Enforcing resolution against the ordered dimensions is the behaviour to look for in a design tool — it is what our design tool does at upload, and it converts an argument three days later into a message at the moment of ordering.
Transparency and edges
Digital printing prints exactly what is in the file, including things the designer could not see. Two problems recur.
A white box instead of transparency. A logo saved as a JPEG has no alpha channel, so its "white" background is white ink or, on a dark garment, a white rectangle around the design. This is obvious in hindsight and invisible on a white artboard, which is where most people check.
Soft or feathered edges. A drop shadow, a glow or an anti-aliased edge cut from a background produces semi-transparent pixels. On a light garment those blend acceptably. On a dark garment they generate a partial underbase and print as a grey halo, which looks like a fault.
Both are checked the same way: open the file on a dark background, not a white one. It takes seconds and catches almost every transparency problem before it reaches a garment. It is also a good reason to refuse JPEGs for logos as a rule rather than case by case.
Check artwork on a dark background. Half of digital print faults are invisible on white.
The white underbase is generated from your artwork
On a dark garment the printer lays white ink first so the colours have something to sit on. In screen printing that underbase is a deliberate separation somebody made. In digital it is generated automatically from the artwork — and it inherits every flaw in it.
Semi-transparent pixels produce a partial underbase. A soft edge produces a soft underbase, which reads as a halo. An area the designer thought was invisible at five per cent opacity produces a faint white patch that is very visible on black.
The underbase is also where most of the ink cost lives, which is why white ink dominates DTG running costs. A design with large solid areas on a dark garment is genuinely more expensive to print than the same design on white, and that belongs in your pricing rather than being averaged away.
Thin lines and small text
Digital printing is not limited by mesh, so the instinct is that fine detail is safe. It is limited by something else: ink spreading slightly into the fabric as it lands.
On a smooth surface a hairline holds. On a knit fabric with visible texture, a line thinner than the weave simply breaks up — parts land on a fibre and parts land in a gap. The same applies to small text, which fills in or goes ragged rather than disappearing cleanly.
Practical limits worth adopting
- Test the smallest text in your typical designs on your typical garment, once, and set a floor from the result
- Expect coarser knits and fleece to need larger minimums than smooth cotton
- Thin light lines on a dark garment are the hardest case — underbase and colour must register
- Check fine detail on the actual garment, not on paper or on screen
- Where a customer insists on small text, print one and show them
Deliberately no fixed number there, because it varies by machine, ink and fabric — and a figure quoted from someone else's shop is worse than the one you measure in yours. The test takes one garment.
The file checklist
Before a digital job goes to press
- Resolution 300dpi at the ordered print size, not at the file's size
- Transparent background with a clean alpha channel — checked on black
- No white box, no leftover background pixels
- Edges reviewed for feathering, glows and shadows
- Fine detail above your measured minimum for that fabric
- Colour profile embedded, and the customer warned that screen ≠ print
- Correct dimensions in inches or millimetres, on the proof
Most of that can be enforced at upload rather than checked by a person, which is where it belongs — a customer told at the moment of ordering experiences it as how the system works, and the same customer told two days later experiences it as an excuse. Whatever is left should appear on the proof as a measured specification, so the print size that resolution was judged against is recorded. The rest of the artwork archive assumes you check the file against the job, not against itself.
