How to Print a Poster?

Increase resolution on this image so that I can make a 12 ✕ 18 print?

A 12-inch by 18-inch looks like a small poster – about 30 cm ✕ 45 cm or approximately A3-paper size, which is the standard drawing book size that I used in elementary school.

Such a small poster would likely be observed on a standard reading distance, which at about 30 cm or one foot away. Hence the recommended resolution would be 300 dots-per-inch (dpi). Refer to this article on how to calculate the the optimal resolution for printing.

With 300dpi, the image would need to be at least 3600 pixels wide by 5400 pixels high, or about 19 megapixels. To put this into perspective, the iPhone 11 back cameras outputs 12 megapixel images, or slightly less than the optimal resolution for this print.

Thankfully there are applications that can enhance images to increase its resolution. Unlike traditional up-sampling techniques like bicubic interpolation, these applications uses machine learning which can “hallucinate” the missing pixels – hence producing sharp details in scales where previous algorithms can only produce blurry outputs.

One of such application is BiggerPicture. This application can enhance images up to 8✕ of the original pixel dimensions without causing blurry or blocky output.

Follow these steps to prepare small poster prints using BiggerPicture.

  1. Load the source image into BiggerPicture.
  2. Choose the Printable tab in the Target Size pane (shown to the right of the image).
  3. Enter 300 dpi in the Print resolution text box.
  4. Drag the slider until the print dimensions meets or exceeds the target real-world size.
  5. Click on the Save all images button.

Enhance Poster for Print

BiggerPicture will then begin the process to enhance your image. This should take about five minutes – depending on the speed of your system.

Now that you’ve got the 19-megapixel version of your image, its time to send it out to a good professional print shop.

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