How to check a picture is high enough resolution for print

Open the Links panel in Layout by Zaweba and select a picture. It shows the picture's actual ppi, which is the resolution of the file itself, and its effective ppi, which is the resolution once it has been scaled to the size it sits in the layout. Effective ppi is the number that matters for print. Live preflight also checks for low-resolution pictures continuously and shows the count in the status bar, so you don't have to remember to look.

A picture that looks crisp on screen can print soft or blocky, because screens show far fewer dots per inch than a printing press needs. Checking resolution before a job goes out is one of the simplest ways to avoid a disappointing print.

Actual and effective ppi

Actual ppi is a property of the file. A photo might be 300 ppi at its original size. Effective ppi changes with how you use it. Scale that photo up to twice its size on the page and its effective ppi halves. Scale it down and it rises.

That is why a picture that was fine for a small spot on page three may not be fine when someone decides it should run across a whole spread. Always judge by effective ppi.

What counts as high enough

There is no single rule, and the right answer depends on the printing method, the paper and how close the reader will be. Your printer is the best source. They will tell you the resolution they want for photos in their process, and that figure is what to check against. Large posters seen from a distance can often get away with less than a brochure held in the hand.

Checking a whole document

The Links panel lists every picture with its status, colour space and size, which makes it easy to scan through. Live preflight does the work automatically. Its profiles include a check for low-resolution pictures, and profiles can be saved and loaded, so a set up that suits one printer can be reused on their next job. Click a problem in the list and Layout takes you to the picture.

Preflight also catches related problems while it is at it: missing or modified links, RGB pictures in a print job and others. A clean preflight count in the status bar before export is a good habit.

Fixing a picture that is too low

The best fix is a better original. Ask the supplier for the full-size file rather than the one from their website or an email attachment, which has often been reduced. If there is no better file, make the picture smaller on the page, which raises its effective ppi. Sometimes a smaller, sharp picture serves the page better than a large, soft one.

Cropping in tightly also enlarges what remains, so a picture that is fine as a whole can fall short when cropped to a detail. The Links panel's effective figure accounts for that, since it reflects the scale in the frame.

A routine for every job

Place pictures linked rather than embedded, so you can swap in better versions when they arrive and the Links panel can show what has changed. Run preflight as you go rather than only at the end. And when you package the job for the printer, the package collects the linked pictures along with the document, fonts where licences allow, and a report, so the printer gets the full-resolution files you checked.

Resolution problems are among the easiest print faults to prevent. A glance at effective ppi and a clean preflight count is all it takes.