Image Resolution for Book Printing

Image resolution tells you how much pixel detail an image has at its final printed size. For book printing, 300 PPI at final size is the standard target for photographs and other raster images.

PPI means pixels per inch. DPI describes printer output, so when preparing artwork, PPI is the number you need to check.

Recommended Image Resolution

Vector artwork does not rely on pixels, so logos, icons, line drawings, and similar graphics are better kept as Vector Graphics when possible. PDF/X workflows commonly use 300 PPI for color and grayscale images and up to 1200 PPI for monochrome raster artwork.

Check Resolution at the Final Size

A file can be 300 PPI and still become low resolution if it is enlarged too much in the layout.

For example:

300 PPI image placed at 100% = 300 PPI

300 PPI image enlarged to 150% = 200 PPI effective resolution

300 PPI image enlarged to 200% = 150 PPI effective resolution

The larger a raster image is placed, the lower its effective resolution becomes.

This matters especially for full-page photographs and images that extend into the Bleed.

Pixel Size and Print Size

The required pixel dimensions depend on the physical size of the image.

A 6 × 9 inch full-page image at 300 PPI needs approximately:

1800 × 2700 pixels

An image does not need the same pixel dimensions when it only occupies half a page. Check the size it actually uses in the layout rather than judging the file only by its total pixel count.

Check Image Resolution in Photoshop

Open the image and choose:

Image > Image Size

Check:

• Width and Height

• Resolution

• Pixel Dimensions

If you only want to inspect the existing image, turn off Resample. This lets you see how print size and resolution relate without adding or removing pixels.

Check Placed Images in InDesign

For images already placed in a book layout, open:

Window > Links

Select the image and check Actual PPI and Effective PPI in the Link Info section.

The Effective PPI is the more useful number for printing because it reflects how large or small the image is actually placed on the page.

Do Not Fix Low Resolution by Changing the Number

Changing a 72 PPI image to 300 PPI does not automatically create real image detail.

If Resample is turned off, changing the PPI only changes the calculated print size. If resampling is turned on, new pixels can be created, but missing detail cannot truly be recovered.

When the original image is too small, using a higher-resolution source is usually the better solution.

Check the Final Layout

Review photographs, scanned artwork, textures, and other raster graphics at their final placed size before exporting the Print-Ready File.

Pay extra attention to images that have been enlarged, cropped heavily, or reused at different sizes. One source image can have a different effective resolution each time it appears in the layout.