Where and how to print your photo mosaic
Published
Your mosaic is a file: print it wherever you like, at the price of the lab you choose. Here is the file to send, the sizes that work and what to check before you order.
In short: order a 20 × 30 in poster (or 50 × 75 cm in Europe) on matte paper, uploading the "photo lab" JPEG that comes with your mosaic. Keep the HD PDF for a professional print shop.
The two files you get
| File | For | What it contains |
|---|---|---|
| Photo lab JPEG | Consumer photo labs, online or in store | The image at the exact ratio of the size you chose, 300 dpi, no margin, no crop marks |
| HD PDF | Professional print shops (posters, large format) | The page with 3 mm (1/8 in) bleed around it, and every small photo in high definition |
Consumer photo labs usually do not accept PDF for posters: they ask for a JPEG or PNG. The PDF is for print shops that trim the paper after printing, hence the extra bleed.
Choose the size
Photo labs sell poster sizes, not A sizes. Choose the same size in the tool as the one you will order, so the file fits exactly.
| Size | Where | Good for |
|---|---|---|
| 16 × 24 in | US | A small wall, fewer photos (100 to 200) |
| 20 × 30 in | US | The recommended size: each photo is recognisable up close, the subject from afar |
| 24 × 36 in | US | A large wall, many photos (400 and more) |
| 50 × 75 cm | Europe | The equivalent of 20 × 30 in |
| 40 × 60 cm, 60 × 90 cm | Europe | The equivalents of 16 × 24 and 24 × 36 in |
| A2, A1 | Professional print shops | With the HD PDF and its bleed |
The larger the poster, the more photos you need so the same photo does not come back too often. The tool shows how many distinct small photos it uses.
Choose the paper
- Matte or satin, 200 gsm or heavier: no glare, the small photos stay readable under a lamp.
- Avoid glossy paper on a large poster, and thin poster paper (under 150 gsm) that curls.
- Canvas or a rigid mount (metal, acrylic) works too: send the same JPEG, at a size the lab offers.
Before you order
- Check sharpness in the tool: the effective dpi should be at least 300, and the HD loupe should show sharp small photos where people will look most (usually faces).
- Check the framing: if the subject's head is too close to the edge, change the framing (top, bottom, left, right) before downloading the file.
- Choose the lab's size in the tool, then download the JPEG: its ratio will match the poster, nothing will be cropped.
- At the lab, turn off automatic colour correction if it is offered: it would change the tones that draw the subject.
- If the lab shows a quality warning, compare the size it expects with the size of your file: a size mismatch is almost always the cause.
A print always comes out a little darker and less saturated than a screen. That is normal, and one more reason to choose matte paper.
A few photo labs
For information only, no partnership: we earn no commission. All of them accept JPEG files and offer the sizes above; compare prices, turnaround and shipping for your country.
- US: CanvasChamp, Nations Photo Lab, Mpix, Printique.
- Europe: CEWE, myposter, Photoweb (France).
Some labs limit upload size (often around 25 MB). The JPEG for a 20 × 30 in poster is about 15 to 20 MB.
Questions
Which file do I send to a photo lab?
The 'photo lab' JPEG that comes with your purchase. Consumer photo labs ask for a JPEG or PNG at the exact poster size, without bleed. The HD PDF is meant for professional print shops.
Which size should I choose?
20 × 30 inches in the US or 50 × 75 cm in Europe: the poster size closest to A2, sold by almost every lab, large enough for each small photo to be recognisable up close.
Matte or glossy?
Matte or satin. Glossy paper reflects the room's light, which makes the small photos hard to read on a large print.
Will my mosaic be sharp?
The tool shows the effective dpi before you buy. Above 300 dpi, each small photo is sharp up close. Check the area that matters to you with the HD loupe before ordering.