If you’ve recently unearthed a huge stack of old family photos and want to scan them, that’s a great decision. But the prospects of doing so can be a little overwhelming for first-time scanners, which can lead to procrastination. And that’s not a good thing because old photos are subject to deterioration and scanning should be done as soon as possible. Before you undertake DIY scanning, it helps to understand the basic terminology that plays an integral role in both the quality of scans and the ability to create nice new prints.
Pixels, DPI, and Resolution
All digital objects are composed of pixels, while printed images consist of dots. Simply put, a pixel (also called picture element) is the smallest unit of any digital image or graphic. Together, they form any visible format on an electronic display. The greater the number of pixels per inch, the better the image quality.
If you zoom in on an image, you’ll start to see the pixels. These colored squares may remind you of that much-played with Lite-Brite from your childhood. When you can see the pixels in an image, this is referred to as pixelated. And this isn’t considered a desirable element in digital or printed photos, unless you’re an artist creating this effect on purpose.
DPI: Short for dots per inch, this term applies to printed images, however, most people also use it for digital images. DPI uses the CMYK (cyan, magenta, yellow, and key/black) color model to determine the amount of red, green, and blue light reflected from white paper. If you intend to print your digital image, you need to pay close attention to the DPI.
The best DPI for scanning photos depends on your intentions. If the image will be displayed on a website only, 72 to 96 DPI should suffice. But if you wish to create new prints, you need to save the image with a minimum DPI of 300 and boost this to at least 600 to make enlargements.
PPI: Short for pixels for inch, you may not have heard of this term because it’s used primarily by design and printing professionals. Just like DPI, the number of pixels per inch determines image quality. PPI utilizes the RGB (red, green, and blue) color model reserved for electronic display of images. This additive color process blends these colors into a single hue at the pixel level.
How to Scan a Photo
To digitize a photo, an image made of dots is converted into pixels (squares). If you looked at a vintage comic book from your childhood, you could easily see the dots and these would get picked up if you scanned one of the pages. That’s because old comic books were generally printed inexpensively with low resolution. Pixels and DPI are the two elements that comprise photo scan resolution. If you wish to increase picture resolution, you need to increase the number of pixels and the DPI. Here’s an example to better illustrate this principle:
- A 4×6 inch image scanned at 72 DPI has a lower resolution than the same size image scanned at 300 DPI, and therefore, is also smaller in kilobyte size. Scanned at 300 DPI, your digital image will be the exact same size in inches as the print and larger in kilobyte size.
JPG is the standard image format on most cameras and smartphones. The best format for scanning photos is typically a JPG or JPEG, as long as you keep compression to a minimum. A TIFF, which is an uncompressed image format is huge in comparison and cannot be displayed online. Professional photographers will often save their best images in both formats.
When choosing a scanner, it’s important to select one that includes the option of scanning at a high DPI. This is typically not an issue with flatbed scanners but can be with dedicated film scanners. Of course, one way to avoid this somewhat confusing issue is to send your precious photos to a professional photo scanning service. At ScanCafe, we scan every photo sent to us by hand, treating each one like it’s one of our own precious memories!