The DPI question: why 150 at final size beats 300 for a wall

The most common file mistake in custom murals is treating a wall like a magazine page. Print culture defaults to 300 DPI because that is the resolution at which a piece held at reading distance looks continuous. A mural is not held; it is read from across a room, and viewing distance changes everything.

The eye can only resolve so much detail at range, so the resolution a surface needs falls as viewing distance grows — the reason a highway billboard is printed at a small fraction of magazine resolution and still looks sharp from a car. For a wall mural seen from several feet or more, an output resolution in the neighborhood of 100 to 150 DPI at the mural's real installed size is standard and reads crisp. Forcing a wall-sized file to 300 DPI rarely improves the visible result and produces files heavy enough to slow every step of production.

The figure that actually matters is total pixels at final size, not the DPI tag written in the metadata. A mural twelve feet wide printed at 150 DPI needs 12 x 12 x 150 = 21,600 pixels across. Run the same math for your own wall and you have the honest spec. A beautiful image that is only 4,000 pixels wide cannot fill a twelve-foot wall sharply at any DPI value, because the pixels simply are not there; relabeling it 300 DPI changes the tag, not the detail.

This is why sourcing and scaling artwork is its own craft. Vector art and repeating patterns scale without loss and are ideal candidates. Photographic and painted sources have to start with enough native resolution, or be enlarged with tools built for the job, before they are committed to a wall. The question to ask any mural file is never 'what is its DPI' — it is 'how many pixels does it carry at the exact size it will be printed.'