Best Image Size for a 3D-Printed Bookmark

The fastest way to get a better 3D-printed bookmark is not a slicer setting. It is the image you start with. A clean crop, enough pixels, and strong contrast give the converter clear edges to trace and give your printer geometry that survives at bookmark scale.

Use this as the source-image checklist before you upload a photo, logo, school drawing, pet portrait, or sketch to ButterySpace's 3D Bookmark mode.

The short answer

For most 3D-printed bookmarks, start with a tall image around a 1:3 aspect ratio. If your bookmark is about 50 mm by 150 mm, a source image around 600 by 1800 pixels or larger is a comfortable target. Higher resolution is fine, but contrast and clean edges matter more than huge file size.

Bookmark size	Shape	Comfortable source image
40 x 120 mm	1:3	500 x 1500 px or larger
50 x 150 mm	1:3	600 x 1800 px or larger
2 x 6 in	1:3	600 x 1800 px or larger
Wide novelty bookmark	1:2.5	700 x 1750 px or larger

Why the 1:3 crop works

Most bookmarks are long and narrow. If you upload a square photo, the tool has to fit that square subject into a tall object. That usually means empty space, cropping, or a design that feels too small.

Crop the image first so the important subject already fits the bookmark shape. Keep faces, logos, names, or drawings away from the very edge. A little breathing room around the subject gives the generated geometry room to become a clean printable object.

What makes a good bookmark image

The best source images are line art: bold outline drawings with clear enclosed shapes, like a coloring book page or an inked sketch. The outlines trace into crisp raised detail, and the shapes between them paint cleanly in your slicer. After that, think silhouettes, logos, simple drawings, pet portraits on plain backgrounds, or well-lit photos with obvious dark and light areas. The common thread is clear separation between the subject and the background.

• Good: bold black line art on a white background, a logo with a strong silhouette, a scanned drawing with thick marker lines, a high-contrast pet portrait, a transparent PNG.
• Risky: a blurry screenshot, a low-light photo, a busy background, tiny text, fine hair, lace, glitter, or subtle low-contrast shading.
• Fixable: a decent photo that needs a tighter crop, brighter highlights, darker shadows, or a simpler background.

Contrast matters more than file size

A 4000 pixel photo can still make a weak bookmark if the subject blends into the background. A smaller but cleaner image often prints better because the edges are easier to trace.

Before uploading, make a quick edit if the photo feels flat:

• Raise contrast so the subject separates from the background.
• Brighten the face or subject if it is underexposed.
• Crop out background clutter.
• Use black-and-white or high-contrast mode for sketches and logos.
• Export as PNG or high-quality JPG instead of a heavily compressed screenshot.

Detail that will not survive

A bookmark is thin and handled often, so very small details are fragile. Fine curls, tiny lettering, eyelashes, faint pencil marks, and small disconnected dots can vanish in the print or turn into weak raised pieces.

As a rule of thumb, if a detail would be hard to see on a bookmark held at arm's length, it may not be worth preserving in the geometry. Simplify the image, crop closer to the subject, or use a bolder version of the artwork.

Recommended workflow

1. Crop first. Aim for a tall 1:3 shape, with the subject centered and not touching the edges.
2. Check pixel size. Around 600 by 1800 pixels is a good target for a normal bookmark.
3. Improve contrast. Make edges obvious before upload.
4. Remove clutter. A transparent PNG or plain background is best.
5. Generate the bookmark. Upload the image in 3D Bookmark mode and download the ZIP.
6. Slice with sensible settings. Use the bookmark print settings guide as your starting point.