What is a rasterbated poster? How halftone dot wall art works

Walk up to a rasterbated poster and it is just dots: big ones, small ones, in a neat grid. Walk to the other side of the room and a face appears. That trick is why the style has stayed popular for twenty years. It is also cheap: black dots on ordinary paper, printed at home.

How halftone works

Printers cannot print grey. They can only put ink down or leave paper bare. Halftone solves this with dots. A dark area gets large dots that nearly touch; a light area gets small dots with lots of white between them. From far enough away, your eye blends the dots and the white into shades of grey.

Newspapers have used halftone for more than a century, with dots too small to notice. A rasterbated poster uses the same idea with dots you can see from across the room, and prints the result across many sheets. The name comes from The Rasterbator, a program from the mid-2000s that made the style popular. The Spolvero tool is not affiliated with it.

Why small photos work

A normal photo poster needs a lot of pixels. Blow a small photo up to a metre wide and it turns soft and blocky. A dot poster does not have that problem. Each dot only needs one pixel from the photo, to decide how big the dot should be. The dot itself is drawn as a vector circle, so it prints sharp at any size.

So a photo 300 pixels wide is already enough for a poster 300 dots across. At 10 mm dots, that is three metres. A photo from a chat app, too small for a normal poster, is fine here.

Choosing the dot size

Dot size decides how far away the picture appears.

Dot size	Best seen from	Look
5 to 8 mm	1 to 2 metres	Closer to the photo, more sheets for the same detail
8 to 15 mm	2 to 3 metres	The classic look for a living room wall
15 mm and up	3 metres or more	Bold and graphic, reads as pattern up close

Smaller dots keep more detail but need more paper to show it. Larger dots make fewer, bolder shapes. The rasterbator poster maker shows a preview at size as you change it.

Black or colour?

• Black dots are the classic look. They are the most striking and need only black ink, usually the cheapest cartridge.
• Colour dots take each area’s own colour. They suit bright pictures.
• A custom colour prints the whole poster in one ink. Try it on pastel paper for a screen-printed look.

The tool estimates the ink before you print, in standard pages, the unit cartridge yields are quoted in.

Which photos work

Contrast is everything:

• Faces with light from one side. The shadow side becomes large dots, the lit side small ones.
• Silhouettes and bold shapes on a plain background.
• Album covers and film stills with dark backgrounds.

Avoid busy, evenly lit scenes, such as a crowd or a landscape in flat light. They turn into an even grey field of dots with nothing to pick out. Crop close: a face that fills the frame reads better than a figure in a wide shot.

Printing and hanging

1. Add the photo, switch the style to dots, and choose the dot size and colour.
2. Set the width in sheets, centimetres or inches.
3. Download the PDF. Every sheet is labelled: rows are letters from the top, columns numbers from the left.
4. Print at 100% or “Actual size”, never “Fit to page”, which shrinks each sheet slightly and stops the dots lining up.
5. Trim the left and top edge of each sheet along the marks, and lay it over its neighbour’s overlap strip. Dots that cross a join line up exactly.

The picture is read and turned into the PDF in your own browser, so it is never uploaded.

For paper choice, glue and hiding the seams, see how to print a large poster on A4. For a normal photo poster rather than dots, the poster maker prints the photo itself, and how big can I print a photo tells you how large it can go before it blurs.