Start with the ratio, not the size
A poster file has a shape, called its aspect ratio. Common ratios are 2:3, 3:4 and 4:5. Each ratio fits a family of print sizes. If the shape of the file does not match the shape of the paper or frame, the print lab or your printer software crops the edges.
Match the file to the print before you order. Here are example sizes for the three ratios most poster sets use:
- 2:3 prints at 4x6, 8x12, 12x18, 16x24 or 24x36 inches
- 3:4 prints at 6x8, 9x12, 12x16, 18x24 or 24x32 inches
- 4:5 prints at 8x10, 16x20 or 24x30 inches
Check that the file is sharp enough
The usual standard for a sharp print is 300 dots per inch at the final size. To find the pixels you need, multiply the print size in inches by 300. An 8x10 inch print needs a file that is 2400 by 3000 pixels.
Some sellers supply one large file that can print at many smaller sizes of the same ratio. Printing smaller from a large file works well. Going the other way does not: raising the dots per inch setting on a small file does not add detail, and stretching it to a bigger size makes it blurry.
To check sharpness before you pay for a print, open the file and view it at 100 percent zoom on your screen. If the edges of the artwork look soft there, they will look soft on paper.
Choose where to print
You have three options: your own printer, a local print shop, or an online printing service. Home printing is the fastest and lets you test a small size first. A print shop or online service handles larger sizes that a home printer cannot take, and many offer paper choices you cannot buy in a pack.
Whichever you pick, upload or load the file as it came. Do not resize it in another program first, because that is where stretching and cropping usually start.
Pick the paper
Use heavyweight paper. Thin office paper curls, shows through and wrinkles in a frame. Heavyweight matte paper or light cardstock holds its shape.
Matte paper gives a softer look with less glare, which suits a wall that gets window light. Glossy paper makes colours look stronger but shows fingerprints. If you cannot decide, ask the print shop for a small sample of each.
Set up the print correctly
At home, open the print dialog and look for the scaling option. Choose Actual Size or 100 percent when you want the layout to stay exact. Fit to Page can shrink the design and shift the margins.
If your printer cannot print to the edge of the paper and the artwork has a border, choose Fit to Printable Area. Then do a test print on plain paper to see what gets cut off before you use good paper.
- Pick the paper size that matches the ratio you chose
- Set the paper type in the printer settings to match what is loaded
- Set scaling to Actual Size or 100 percent
- Print one test on plain paper
- Print the final copy on your good paper
Mistakes to avoid
These are the problems people run into most often with digital downloads. Each one is easy to avoid if you check it before you print rather than after.
- Ignoring the ratio, which leads to cropped edges
- Stretching or squeezing the image to fill a different size. Crop or add a border instead
- Using a low resolution or heavily compressed file, which causes blur
- Expecting the print colours to match the screen exactly. Colour can vary with screen and printer settings, so check a test print
- Skipping the size guide that came with the files