Printing4 min read
DTF print file requirements: size, DPI, format and colour
What a DTF printer needs from your artwork: a transparent PNG or a PDF, 300 DPI at the printed size, solid edges and the right dimensions. With a free tool to check a file.
By the Quaflow team
A DTF (direct-to-film) printer does exactly what the file tells it to. It prints the design on a film in colour, lays white ink over it, and the transfer is heat-pressed onto the garment. There is no step in between where someone tidies up the artwork, so a low-resolution logo prints as a blurry logo, and a white background prints as a white box.
This guide covers what a file needs before you send it, and how to check each point.
Free toolDTF Print File CheckerDrop a PNG, JPEG or PDF to check its size, resolution, transparency and gang sheet fit. The file stays in your browser.
Use a PNG with a transparent background, or a PDF
DTF prints only the pixels that are in the file, which makes transparency the most important property of a design.
| Format | Transparency | Good for |
|---|---|---|
| PNG | Yes | Almost everything: logos, illustrations, photos cut out from their background |
| Yes | Vector artwork and text that must stay sharp at any size | |
| JPEG | No | Rectangular photos only: the background always prints |
If your design sits on a white or coloured canvas, remove that background in your editor and export a PNG. A background that looks invisible on a white screen is very visible on a black T-shirt.
For a PDF, embed the fonts or convert text to outlines. A missing font is replaced by another one on the print shop's computer, and the layout shifts.
Print at 300 DPI
Resolution decides how sharp the print is. The usual target is 300 DPI at the size you print. Bold designs with large shapes still look good at around 200 DPI. Below about 150 DPI the pixels become visible.
The important words are at the size you print. The DPI value saved in a file is only a note. What counts is how many pixels the design has compared with its printed width:
resolution = width in pixels ÷ printed width in inches
A design that is 3,000 pixels wide prints at 300 DPI when it is 10 inches wide, and at 150 DPI when it is stretched to 20 inches. Enlarging the image in an editor doesn't help: it adds pixels but no detail.
| Printed width | Pixels needed for 300 DPI | Typical use |
|---|---|---|
| 3 in | 900 px | Sleeve or pocket logo |
| 4 in | 1,200 px | Left chest |
| 10 in | 3,000 px | Standard front |
| 12 in | 3,600 px | Large front or back |
Size the canvas to the design
Many files are saved on a canvas that is bigger than the artwork: a 4 inch logo in the middle of a 12 × 12 inch square. Print shops price by area, and some print the whole canvas size, so those empty margins can cost money or shrink your design.
Crop the canvas to the edges of the design before you export. If you want to know how large the design really is inside a file, the print file checker measures the visible area without the transparent edges.
Check the width as well. Most DTF roll printers print 22 inches across on 24 inch film, so a design wider than 22 inches in both directions has to be printed smaller or split.
Keep the edges solid
DTF lays white ink under every visible pixel so that colours stay bright on dark fabric. That works well for solid shapes and badly for anything half transparent. Soft drop shadows, glows, smoke and edges that fade out tend to print as a pale, milky haze, because the white layer shows through.
Three ways to avoid it:
- Use hard edges and remove soft shadows and glows.
- Turn gradients that fade to nothing into a halftone, where the fade is made of small solid dots.
- After removing a background, zoom in and delete the faint leftover pixels around the design.
Mind thin lines and small text
Very thin lines may not hold enough adhesive to stick to the fabric and can peel off after a few washes. As a general guide, keep lines at least about 0.02 inches (0.5 mm) thick and avoid text smaller than about 8 points. Print shops differ here, so check your provider's minimums for fine detail.
Leave the colour conversion to the print shop
Send RGB files unless your print shop asks for something else. Their printing software converts the colours to the printer's inks and builds the white layer. Colours on a backlit screen are brighter than ink on fabric, so very saturated greens, blues and neon tones will print a little duller. If an exact colour matters, ask for a test print.
A checklist before you send the file
- The background is transparent, and the file is a PNG or a PDF.
- The resolution is 300 DPI at the printed size, or at least 150 DPI for bold designs.
- The canvas is cropped to the design.
- The design is no wider than 22 inches in at least one direction.
- Edges are solid, with no soft shadows or glows.
- Lines and text are thick enough to survive washing.
When several designs or many copies go into one order, they are usually combined on a gang sheet. The gang sheet calculator shows how many copies fit on each sheet size.