There are dozens of different types of image files. You've probably seen many of them online: PNGs, JPGs, PSDs, TIFs, and of course the meme centric GIFs. Have you ever wondered, what are the differences between all these file types? Well, I have the answers! Below is a brief explanation of what each file type is and when to use each type.
To start, there are two main categories of image files that are relevant for our discussion. Compressed and uncompressed.
JPEG: You may not know this, but JPEG is actually an acronym for "Joint Photographic Experts Group". The JPEG format was introduced in 1992, and it is the default image file type, and the most common you will find today. JPEGs are so common because they do a lot of things very well. JPEGs can maintain great image quality, they are easy for computers to process, they are compatible with just about EVERY device, and they don't result in huge file sizes. JPEG files are compressed, meaning that the computer or camera generating the file throws out data that it considers to be unnecessary (this is called "lossy compression" because data is lost). Like an MP3 file, this is meant to make the file size easier to manage, while also retaining high-enough quality that most people don't notice the missing image information. Unless you are a professional photographer or an image nerd, your smartphone and camera are probably set to shoot JPEG images, and they will work just fine for normal use.
PNG: PNG is also an acronym, it stands for Portable Network Graphics. According to Wikipedia, these were created as a "free, open-source alternative to GIF". PNGs support many more colors that GIFs and can result in much higher-quality images. PNG is a compressed format like JPEGs, but it uses a different method for compression that is considered "lossless". That means that while PNG images are compressed, that compression does not actually result in any loss of detail or image data. When an image is mostly uniform (such as a graphics file with just a few colors), PNGs work well. With regular photographs, JPEGs result in smaller files without a noticeable difference in quality, which is why PNGs are not the default. PNGs are more common for images on the web, whereas JPEGs are what most people are posting to social media and sharing with friends.
GIF: Graphics Interchange Format images, or GIFs, are lower quality image files that have been around since the dawn of digital images. Developed in 1987, this image format is older than many of the people sharing memes on social media. GIFs main claims to fame are that it supports animations, and has small files sizes, which is why it's so widely shared on the internet. GIFs technically use a lossless compression technique, but they only support 256 colors per image, so normal photographs converted to GIF format look very low quality. This image format is really only for sharing animations on the web, or for creating small graphics files.
HEIF: High Efficiency Image File Format (HEIF) is like JPEG but on steroids. This is a relatively new image format that is still not very common, the development was finalized in 2015 according to Wikipedia. There are some big names throwing their weight behind this format, including Apple (which uses HEIF as the image format for iPhone photos). HEIF allows for photos that are much higher quality than JPEG, without increasing the file size. They also support animations (like Apple's Live Photos feature on iPhones), giving them a big advantage over JPEG. Many older devices, such as older smartphones and cameras, cannot read HEIF images, which is part of why they are not yet too widespread. In the coming years, expect HEIF to become the default image type instead of JPEG.
PSD: Photoshop Documents are a bit of a niche file format, anyone who works with Adobe's Photoshop software will be familiar. PSD files are really considered "documents" and not "images" per se, because they can keep track of all the details you can manipulate in Photoshop like graphics, text, transparencies, multiple layers, and even information that isn't visible in the image. These files can be HUGE, up to 2 GB, and can hold extremely high resolution images. PSD files are really only used for working in Photoshop. Once you are ready to share a photo through the web or archive it, most people convert to a different (smaller) format.
TIFF: Tiff stands for "Tagged Image File Format", and it is a very high-quality image format (lossless) that is widely used by photographers to store archived versions of their original photos. This is why many photographs refer to TIFF files as "digital negatives", they contain all of the information captured by the camera in the original photograph. TIFF files are widely compatible with many difference devices, as they are also a popular format for scanners and document readers, and they support layers like PSD files. Many of my files are saved in TIFF format, and in fact when you use my print and negative archiving services, you will receive TIFF files in return. I prefer this format because it is widely readable by most computers, very stable, and maintains very high quality. They are also very easy to convert to JPEGs without having to use special software.
RAW: RAW images files are more of a category than a specific image type. RAW images are the uncompressed images that come out of higher end cameras, such as DSLR's from Canon and Nikon. Each camera manufacturer uses their own format, but they are largely similar. Like TIFFs, RAW photos are considered to be "digital negatives" because there is no compression, so they have all the information that the camera could capture when it took the photo. RAW files are what photographers start off editing in photoshop (though many will save them as TIFF files afterwards). If you are serious about taking photographs, change the settings in your camera so that you are shooting RAW files (beware though, they take up A LOT of space!).
That's just a brief rundown of some of the most common image types. There are actually dozens more that are less popular and have specific uses (did you know there is an extra large type of Photoshop file called a PSB?). I encourage you to learn the basic differences between these file types, to make sure that you are choosing the correct one for your project! A basic rule of thumb to keep in mind is: RAW/TIFF files to archive and save, JPEG photos to share with friends and via email, and GIFs for animations.