To make sure your prints come out sharp, detailed and professional, check your image file before you upload it. Three things decide the result: the resolution, the colour profile and the file size.
1. Resolution (DPI)
DPI means dots per inch. It tells you how many pixels your file has for every inch of the finished print. This is the single biggest factor in how sharp your print looks.
Printumo produces print files at two different resolutions:
Fine art paper prints: 300 DPI. Paper prints are viewed close up, so they need the higher resolution.
Canvas prints: 150 DPI. The texture of the canvas softens fine detail, and canvas is normally viewed from further away, so 150 DPI is enough.
To work out the pixels you need, use this formula: pixels = (centimetres ÷ 2.54) × DPI.
For example, a 30 x 40 cm fine art paper print needs 3,543 x 4,724 pixels. The same size printed on canvas needs 1,772 x 2,362 pixels.
2. The quality dot in the product editor
You do not have to do the calculation yourself. After you upload your artwork, every print size shows a coloured dot. The dot tells you how well your file performs at that size.
Fine art paper
Dark green (great): 300 DPI or more
Green (good): 200 to 299 DPI
Amber (average): 150 to 199 DPI
Red (poor): under 150 DPI
Canvas
Dark green (great): 150 DPI or more
Green (good): 75 to 149 DPI
Amber (average): 50 to 74 DPI
Red (poor): under 50 DPI
The dots inform you, they do not block you. You can still offer a size that shows an amber or a red dot, but we recommend that you do not.
3. Colour profile
Use the sRGB colour profile. sRGB is the standard for print on demand, and it keeps your colours consistent across screens and prints.
Other profiles are accepted. Adobe RGB has a wider gamut, and CMYK files work too, but both can shift in colour when they are converted. Convert your file to sRGB before you upload it to avoid surprises.
Everything is printed in sRGB. Whatever profile you send, we convert it to sRGB for printing.
4. File size
File size on its own tells you very little, because it depends on the file format and the compression as much as on the pixels. Use the pixel dimensions above as your guide instead. Two limits are still worth knowing:
A very small file, for example under a few MB for a large print, usually means low resolution or heavy compression.
Uploads are capped at 150 MB, and at 100 MB for PDF. A file above that limit is not a better file. It is normally uncompressed, layered, or saved at 16 bits per channel, and none of that reaches the paper.
Quick checklist before you upload
Does the file have enough pixels for the largest size you want to sell? Use 300 DPI for paper and 150 DPI for canvas.
Is the colour profile sRGB?
Is the file a flattened JPEG, PNG, TIFF or PDF, and under the size limit?
Are the quality dots green for every size you plan to offer?
Need help checking your file?
If you are unsure about your file, send a message to Printumo Support with the file attached. Our team will review it for you before you launch your product.