How to prepare a poster for print

Print is unforgiving in ways screens are not. The sheet is cut with a small margin of error, ink is duller than light, and a photo that looked fine on your monitor can print as mush. Everything below exists to close those three gaps. You can do all of it in any competent design application; the last section shows the route in Voidcanvas.

What you will need#

• The final size of the poster. If you are not sure, A3 (297 × 420 mm) is the usual notice board size and A2 (420 × 594 mm) the usual wall size. In the US, 18 × 24 in is the equivalent of A2.
• The printer's specification: how much bleed they want (nearly always 3 mm, or 0.125 in), whether they want crop marks, and whether they accept RGB. Ask before you start; a two-line email saves a reprint.
• Your images at full size. A photo for an A3 poster needs to be about 3500 px on its long edge to fill the width at 300 dpi. Phone photos are; images saved from the web are not.
• The words, checked. Dates, prices and web addresses are the things that get reprinted.

Try the setup before you read the rest#

Pick a size and flip the three settings that decide whether a poster prints well. The sheet on the left is what comes back from the printer if the cut drifts by a millimetre, which it will. The close-up is a 30 mm square at print scale.

The correct document setup#

Work at the final size from the start. Scaling a finished A4 up to A2 doubles every pixel and softens every photo. The table gives the pixel size of each common poster at 300 dpi, and the size with 3 mm bleed added on every side (36 px each side at 300 dpi, so 72 px on each dimension).

Use the calculator for any other size, in millimetres or inches.

Resolution#

Resolution only matters for photos and textures; type and flat shapes drawn in the application are sharp at any size. The rule: a photo should have at least as many pixels as the area it covers at 300 dpi. A photo that fills the width of an A3 poster needs about 3500 px; one that fills a quarter of it needs about 1750 px. Check by viewing the photo at 100 per cent at the document's size and looking at an edge. If it is soft there, it will be soft on paper. Enlarging a small photo does not add detail, it only smooths the softness. Image resolution explained has the maths and the fixes.

Bleed#

Bleed is artwork that runs past the trim edge so the guillotine, which drifts by up to a millimetre, still cuts into colour rather than into white paper. Anything that touches an edge (a background, a photo, a stripe) must continue 3 mm beyond it. Anything that does not touch an edge needs nothing. Crop marks are the short lines outside the bleed that show where the cut goes; the printer usually adds them, and if you add them yourself they must not touch the artwork.

Safe area#

The same drift that makes bleed necessary can slice into a phone number set close to the edge. Keep text, logos and anything that would look wrong cut at least 5 mm inside the trim (59 px at 300 dpi). On a poster, 10 to 15 mm looks better anyway: a wide margin reads as confidence, a tight one as a mistake.

Colour#

Screens make colour with light (RGB) and presses make it with ink (CMYK), and ink cannot reach the brightest blues, greens, oranges and pinks a screen can show. Someone converts your file, and the best person to do it is the printer, with the profile for their press and paper. So work in RGB, avoid building the design around a neon that will not survive, and ask for a proof if the colour matters. Two things to ask about: whether black text will print in black ink only (a generic conversion can turn it into a four-ink mix that looks fuzzy), and whether large black areas should be a rich black. Colour that works covers how to plan a palette that survives the trip.

Typography#

Posters have three levels of type: the one thing (event, product, headline), the facts (date, place, price) and the small print. Make each level clearly different in size, not slightly different. A poster is read at two distances: the headline from across the room, the facts from a metre. As a rule of thumb, small print on a poster should not go below 18 pt (about 75 px at 300 dpi), and the facts sit comfortably at 30 to 48 pt (125 to 200 px). Points are 1/72 of an inch, so at 300 dpi one point is about 4.2 px, which is why type that looks big on a zoomed-out canvas can be tiny on paper. Typography fundamentals explains scale, measure and spacing.

Images#

• Place photos at 100 per cent or smaller, never enlarged. If you must enlarge, stop at about 120 per cent.
• Crop hard. A poster is a single image seen from a distance; a wide photo with a small subject reads as nothing.
• Lift the shadows a little for uncoated paper, which absorbs ink and fills dark areas in. On coated stock, leave them.
• Sharpen once, gently, at the final size, as the last step before export.
• If the only photo you have is too small, make that the design: a coarse halftone, a duotone or a heavy crop turns low resolution into a treatment rather than a defect.

Export settings#

Export a PDF at the final size including bleed. If your application offers PDF/X-1a or PDF/X-4, use it; if it offers only a plain PDF, that is fine for a poster, as long as the page size is right and images are not downsampled below 300 dpi. Keep a PNG at the same pixel size as a fallback: some large-format printers prefer it. Do not send a JPG of the poster; JPEG compression softens type.

Printer checklist#

• Page size equals the trim size plus bleed, and the printer knows which is which.
• Every photo checked at 100 per cent at document size; nothing enlarged past 120 per cent.
• Text and logos at least 5 mm inside the trim; nothing important within 10 mm of a corner.
• Backgrounds and photos run to the bleed edge, not the trim edge.
• Small print at 18 pt or more. Every date, price and URL read aloud by a second person.
• The file is RGB and the printer has confirmed they will convert it, or you have converted it to their profile.
• A proof requested for anything with a photo of a person or a brand colour.
• The email to the printer says: size, bleed, RGB or CMYK, crop marks or not, paper and quantity.

How to do it in Voidcanvas#

There are two routes. Use the Editor when you want to design the poster by hand and are happy to add the bleed yourself; use Studio when the poster is one format in a client job and you want bleed, crop marks and a slug line added for you.

In the Editor

1. 1On the start screen choose Poster 18 × 24 in (5400 × 7200), A4 flyer (2480 × 3508), or type a custom size from the table above, for example 3508 × 4961 for A3.
2. 2Before you design, add the bleed: Image, Canvas size…, tick Relative, enter 72 in Add to width and 72 in Add to height, anchor in the centre, Apply. Nothing is scaled; the canvas grows by 36 px on each side.
3. 3Add guides for the trim and the safe area: View, New guide… at 36 px from each edge for the trim, and again at 95 px (36 + 59) for the safe area. View, New guide layout… puts a column grid inside them if you want one.
4. 4Design. Run the background and photos to the outer edge of the canvas. Keep type inside the inner guides. Check photos at 100 per cent with Ctrl+1 (Cmd+1 on a Mac).
5. 5Export with Ctrl+E and choose PDF. Because the design is over 2000 px on its longest side, the page is sized at 300 dpi, so an A3 with bleed comes out at 303 × 426 mm. Leave Size at 1× and Quality high.
6. 6Send the PDF with the note: "RGB, 300 dpi, 3 mm bleed included, no crop marks."

In Studio

1. 1Open a job and, on the Brief tab, add a print format: A3 poster, Poster 18 × 24 in or A4 flyer. Each knows its size in millimetres.
2. 2Build the design on the Key visual tab, or send it there from the Editor.
3. 3On Deliver, tick Print PDF and choose Build the package. The PDF is at trim size with 3 mm bleed made by extending the artwork's edges, crop marks outside the bleed, TrimBox and BleedBox set for the printer's software, and a slug line recording the job, version, size, bleed and that the file is RGB.

Common mistakes#

• Designing at screen size and scaling up. A 1080 px social post enlarged to A3 is 92 dpi. Start at the print size.
• Adding bleed by stretching the finished design. That moves the safe area and enlarges the photos. Add canvas, then extend the background.
• White hairline on one edge of the printed poster. No bleed, or the background stopped at the trim.
• Colours came back dull. Expected for bright RGB. Ask for a proof next time, and see the colour section above.
• The PDF opened at the wrong size. In the Editor, a design 2000 px or smaller on its longest side is treated as a screen document at 96 dpi. Posters are always bigger than that; business cards are not.
• Very large exports fail. Browsers cap image size. Exports over about 67 megapixels (an A1 at 300 dpi is 70) are scaled down to fit. Use 150 dpi for A1 and above.

Quick checklist#

• Final size, 300 dpi (150 for A1 and up), bleed added as canvas.
• Guides at trim and safe area; type inside the inner one.
• Photos checked at 100 per cent.
• Three type levels, small print 18 pt or more.
• PDF at final size; printer told RGB, bleed, marks.

Open the Editor