Preparing an image for print versus screen

The image looks sharp and bright on your screen. You send it to a printer, or to a print shop, and what comes back is smaller than expected, slightly soft, darker than it looked, and with a sliver of the edge missing.

Screens and paper work differently, and an image prepared for one is usually wrong for the other in four specific ways.

1. Resolution: pixels need a physical size

On a screen, an image is just a number of pixels. The screen decides how large they appear.

On paper, each pixel has to be given a physical size. That is what PPI — pixels per inch — describes. (People often say DPI, which strictly refers to the printer's ink dots, but in everyday use they mean the same thing.)

The rule of thumb:

• 300 PPI for prints viewed up close — photographs, flyers, anything held in the hand.
• 150–200 PPI is usually acceptable for larger prints viewed from a little further away.
• Posters and banners viewed across a room can go lower still.

So the question is always: how many pixels do I have, and how large do I want it?

Print size in inches = pixels ÷ PPI.

A 3000 × 2000 pixel photo at 300 PPI prints at 10 × 6.7 inches (about 25 × 17 cm). At 150 PPI, it prints at 20 × 13.3 inches, but less sharply.

The PPI number stored in a file — "72 dpi" or "300 dpi" in its info — does not change the pixels at all. It is only a hint about print size. Changing it from 72 to 300 without resampling makes the same image print smaller, not sharper.

2. Colour: screens glow, paper reflects

A screen emits light; paper reflects it. Printed images almost always look darker and less saturated than the same image on a bright screen, particularly in the shadows.

Three things help:

Turn your screen brightness down when judging an image for print. Most screens are set far brighter than paper looks under room light.

Lift the shadows slightly for print. Detail that is visible on screen in dark areas often turns to solid black on paper.

Keep the image in sRGB unless the printer asks otherwise. Home printers and most photo labs expect sRGB. Professional offset printing works in CMYK, and a print shop will either convert your file or ask you to supply CMYK. Ask them — do not guess.

Vivid screen colours — bright blues, saturated greens, neon oranges — may not be printable at all. They come out duller. That is not a fault with your file.

3. Bleed: printing to the edge

Printers cannot reliably print right to the edge of the paper, and trimming machines are not perfectly precise.

For anything that should run to the edge, a print shop will ask for bleed: the image extended beyond the final trim size, usually by 3 mm (about 1/8 inch) on every side. After printing, the sheet is trimmed, and the extra is cut off.

They will also ask you to keep text and important elements a few millimetres inside the trim — a safe zone — so nothing is lost if the cut wanders.

A 10 × 15 cm postcard with 3 mm bleed is supplied as 10.6 × 15.6 cm.

4. Format: what to send

For screens: PNG for graphics and text, JPEG for photographs, at the exact pixel size needed.

For home printing: a high-quality JPEG or PNG at full resolution, sized in the print dialog to the paper.

For a print shop: usually a PDF, or a high-quality TIFF or JPEG, with bleed included, at the size and resolution they specify. Their requirements page is the authority.

One source, two outputs

The practical routine:

1. Keep a master at the highest resolution you have, with layers if you used them.
2. Export a screen version at the exact pixel size needed.
3. Export a print version at the print size and resolution required, with any adjustments for print — lifted shadows, bleed — made on a copy.

Never print from the screen version. It has been resized down and cannot be enlarged back without losing sharpness.

Printing on a Mac

Preview prints directly with a useful Scale and Paper Size preview, and Photos offers print layouts for standard photo sizes. Both are fine for home prints of photographs. For anything with bleed or layout, you need an editor that works at a specific physical size.

What Miyu Paint does

Miyu Paint is a native image editor for Mac. Its free tools open, crop and resize images and draw on them, and export PNG or JPEG up to 2048 pixels on the longest edge, with no watermark. That is ample for screens. For print it is a real limit: 2048 pixels at 300 PPI is just under 7 inches, or about 17 cm, on the long side.

Full access removes the limit with full-resolution export, adds printing and advanced formats, and brings layers, adjustments and editable .mpaint projects — so one master can produce both the screen and print versions without redoing work. Full access comes from a fourteen-day trial that you start yourself and that never renews into a charge, or a one-time Lifetime Unlock.

Editing happens on your Mac, with no account, advertising, analytics or tracking.