Many of us who print images from home notice that some pictures tend to print in lower quality than others. This is because different image types interact differently with printing software due to their quality.
The next time you print, look at the file extension. Do you notice the .JPEG (or .jpg) extension? What about .png? These stand for specific kinds of encoding: JPEG stands for Joint Photographic Experts encoding, while PNG stands for Portable Network Graphics encoding. Both have strengths and weakness depending on the application and what you need to do with them.
Here we’ll break down these file formats and discuss how thy impact digital printing.
What is Digital Image Encoding?
When computers render images on your screen, they need information that tells the monitor what colors to put where. In the early days of image displays, these pictures were simple and crude because monitors couldn’t handle in-depth colors and complex shading. Modern monitors, however, can, which means that a single image can be extremely huge just to store all the color information needed to display it properly.
That’s why digital imaging experts have come up with several ways to encode image data so that it can be viewed by everyone. Digital image encoding means taking that color and display information and coding it so that different computers and software can display them. Some encoding schemes are highly specific for high-end software and workstations (think Adobe Photoshop) where other schemes, like JPEG and PNG are purpose-built to be viewable across numerous computers easily.
What is a JPEG File?
A JPEG image is “compressed” in what is called a “lossy” method. What this means is that the software algorithms used to encode the image (usually converted from another image) actually discards some information regarding color and shading to make the file smaller (compressing it). This fools a regular viewer by eliminating areas where color changes wouldn’t be noticeable to the naked eye while reducing image quality overall.
Think about the pictures you take with a digital camera: they typically start as RAW image data, meaning they are really high-quality images that are extremely large. Most cameras allow you to compress these into JPEGs which makes them easier to share, store, and view.
What is a PNG File?
A PNG, contrasted to JPEG, is uncompressed. What this means is that they are much higher-quality than JPEGs while having a much larger size. PNG files also include enough space to store data for transparency and opaqueness as well as high levels of color depth and shading.
Typically, PNG files can be converted to JPEG files with a loss of quality. However, converting a JPEG to a PNG will retain the lower-quality compression of JPEG, so many media providers who use high-quality images will have source PNG files that they can produce compressed JPEGs from, depending on their needs.
Which is Better for Printing?
In some many home cases, JPEGs are fine for printing. You may notice some loss in quality depending on how you size the image: small JPEGs that aren’t meant to scale in size will warp and shrink when they aren’t in a native size and will look terrible for printing.
However, a PNG file, properly sized, will look beautiful printed because they retain so much data on color and size.
If you want to print a high-quality image—printer and paper quality notwithstanding—look for PNG images.