Designers working on different marketing materials have to scale an image to support a variety of size outputs without compromising the image’s resolution. The resolution is affected by the DPI or dots per inch that make up the image when printed. Commercial printers will give designers recommendations on resolution and scale to get their desired outcome.

For a large poster, it’s recommended to have 300 DPI, however as low as 72 DPI is still acceptable. Most designing programs like Photoshop, Illustrator, or InDesign will be able to save your file in 300 DPI before sending to print.

Let’s look at some factors to look out for when designing large-scale prints and which file formats are preferred for printing these images. Keep reading for some printer recommendations and a reference guide for size and resolution.

What to Look Out for in Your Image Before Printing

Working on a large-scale image for a poster in a design program that requires you to scale the image down to edit it gives you a warped view of the overall quality of the image. The poster may look perfect when scaled down but may have some issues when scaled back to its intended size.

Pixelated Edges and Noise

The primary thing you want to look out for is pixelated edges and noise. Noise means any variation of color or brightness within an image, and even high-resolution images can be affected by noise. For example, a light blue sky can appear splotchy in places when printed at the large scale required.

The solution to cleaning up the noise in the image is locating the areas, zooming in, and then blurring out the noise. The same method can be used to fix pixelated edges.

Color Mode

Before sending your image to be printed, you always want to ensure that the color mode for your image matches the color mode the printers will use to print your image. If not, you could end up with a poster with variations in color as the ink jet printer will use its standard color mode to match the color mode of your image.

Printers use the CMYK color mode, and monitors display RGB. The color mode depends on what you want to do with your image, and certain design programs have a default color mode that may need to be changed to suit your needs. If you’re putting the image on the web, then RGB color mode is the way to go, but if you’re printing the image, set the color mode to CMYK.

What File Format Should You Use to Print Your Poster?

File formats may seem like a no-brainer, but certain file formats could delay your product. File formats like .eps, .psd, .bmp, .doc, etc. require manual submission with some printers and extra processing time.

The most common file formats to use when sending your image to be printed are .jpg, .pdf, and .tif. You should always double-check with your printers to ensure those file formats are accepted.

File formats aren’t the only factor you should be concerned about before sending your image to be printed. Size, resolution, and proportions (aspect ratios) ensure your image is printed at the desired quality and scale.

What Size and Aspect Ratio Do You Use for Your Poster?

The size and aspect ratio depend on your poster’s desired output size. Take your desired output size and divide both sides by 4 to get your needed original file size. Your submission file size will be affected if you want a high-quality image at 300 DPI.

If the desired DPI is 300, the rule of thumb is to do 25% of the desired final output size. If you use the same formula for aspect ratio, you will get the correct document size for 300 DPI.

Conclusion

When working with large-scale images for marketing materials like posters, it can be confusing to know how to prepare your document in the best way for your printers to get the desired finished product. Now you know what factors to double-check, what file formats are best, and the correct size and proportions for high-quality resolution.