High resolution + Low resolution: What You Need to Know

 Maybe you’ve encountered the terms “high resolution” and “low resolution” in discussions about digital photos. Here’s what you need to know.

The term resolution (res for short) is used in both the digital and print world.

Image resolution denotes the detail an image possesses. Low-resolution images (also known as low res) contain less information, signifying fewer pixels (in digital form) or dots (in print) per square inch.

High-resolution images encompass more information. Pixels per inch (PPI) or dots per inch (DPI) gauge the sharpness of an image.

A helpful definition shared by a colleague is that the term DPI (dots per inch) is exclusive to printing. Whenever you scan something (be it a photo, transparency, document, artwork, etc.), you are converting something with physical dimensions to pixels; thus, PPI (pixels per inch) is the correct technical term.

Low-res digital images, which you may have encountered, exhibit a certain level of pixilation, sometimes presenting as compile boxes or squares pieced together (as illustrated in our example).

Online and web graphics, set at 72 PPI, appear satisfactory on a computer screen at their display size. However, printing them would yield a pixelated appearance – something to avoid.

Choosing a high-resolution image at 300 PPI with a one-to-one dimension (the industry standard for printing) would be a much preferable option.

What purposes do low-res files serve?

As mentioned, low-res files are suitable for screens – on social media, websites, and smaller digital frames. If you send or receive photos via apps like Instagram and WhatsApp, those are low-res files.

Moreover, several online photo sites, such as Shutterfly, compress any hi res files uploaded to their site. Consequently, if you attempt to retrieve them, you will typically receive back low res files. This situation is less than ideal, if those are your only copies (and if you are a user of Shutterfly Share Sites, please be aware that Shutterfly will be discontinuing the Share Sites service in March 2023).

What purposes do hi-res files serve?

When capturing photographs (via a smartphone or DSLR), effective resolution starts around 300 PPI and increases from there. All smartphones auto-generate hi-res files from your photos.

As a result, these photos look superb when printed or framed. Hi-res files are perfect for enlarging to a considerable extent and cropped without losing much detail. This is crucial when creating printed products such as photo books. You can use low-res images, but they need to be small – matchbox size – for easy viewing.

Most photo collections combine low-res and hi-res files. When eliminating duplicate digital photos, it is always preferable to delete the lower resolution versions of images.

When digitizing print materials, we employ a process called camera scanning, which results in higher resolution archival-quality scans. These hi-res files are perfect for print reproduction.

35mm slides and negatives, being much smaller originals, are output at a high PPI (2400), making the digital versions clear and viewable at roughly 8 times the size of a slide.

The scanner allows for enlarging prints smaller than 8×10″ at 600 PPI up to 200% when printing. For example, a 3×5” photo scanned at 600 PPI can be printed at 6×10”. These higher resolution files are ideal for long-term preservation as well