JPEG, PNG, GIF, TIFF, raw? Or Do I Look Like I Know What a JPEG Is?
Let’s assume you are a simple propane salesman and you desperately need a picture of a hot dog. You go to your favorite stock site, dreamstime.com, and find an image of a tasty looking hot dog. You are then given a bunch of options for download: A JPEG, PNG and a TIFF. Why are there so many different options?
Before talking about specific file types, let’s talk about compression. Bandwidth isn’t free, so transmitting huge bitmap files isn’t very efficient. Most image files employ some form of compression, which can be lossless or with loss. Lossless compression is reversible, but has the disadvantage of larger file sizes and more resource-intensive decoding. Lossy compression has an irreversible effect on the image quality but file sizes are smaller.
JPEG is the acronym of its creator, the Joint Photographic Experts Group, and refers to the compression method it uses. JPEG compression is used in different image formats such as JPEG/Exif and JPEG/JFIF, but most people call all of them just JPEG. Most cameras can output some form of JPEG file and it is the most popular image format out there. JPEG compression works by discarding some of the color data and detail in the image. The amount of compression can be adjusted; large amount of compression has a more severe effect on the image quality. JPEG images store color information in 24 bits, or 8 bits per channel. Different color spaces can be used, but sRGB is the most widely adopted and supported.
GIF (pronounced however you like), or Graphics Interchange Format, is a file format associated these days with animations. Technically animation support came later; the original purpose of GIF was to display logos and simple illustrations without loss of quality over the web and in BBSs. It is a lossless format, but traditional GIFs only support 8-bit color, which makes it less ideal for displaying photos. GIF files can be large, and there are arguably better video file formats out there, but it is widely supported and popular for example in social media.
PNG is another popular file type and stands for Portable Network Graphics. PNG files employ a lossless compression and 24-bit color plus additional alpha channel for transparency. PNG was intended to be an open-source replacement for the GIF file format, but doesn’t support animations. PNG works well with photographs and has wide support but doesn’t compress files as much as JPEG, which can be seen as a downside when transmitting image files in the internet.
EPS stands for Encapsulated PostScript, and is a familiar file type for illustrators. All previous formats mentioned here are raster graphics, which means they store the image information in a dot matrix format. EPS is a vector format, which means the image can be scaled freely without loss of quality. Technically an EPS file is a program which describes how the image can be reproduced and contains a “preview” of the image encapsulated in it.
TIFF, or Tagged Image File Format, is popular among photography and graphics industry professionals. TIFF files are actually containers that can hold uncompressed and/or compressed file data, vector information, clipping data and more. Apart from animations, you can basically store whatever you want in a TIFF file. The downside is that TIFF file sizes can be much larger than other file formats and you might not have the correct tools to open what’s inside the container. Old joke is that TIFF stands for “Thousands of Incompatible File Formats”.
Last but not least is the raw file. As the name suggests, this is not a real name or a file extension, but refers to the data being in “raw” format. Raw files basically contain the unprocessed data coming from the sensor of a camera. Each camera maker has their own raw file format and you need the correct codecs (coder/decoder) on your computer to edit the files. These usually come with the camera, can be found on the website of the camera maker or are included in the darkroom software. Raw files are large but contain all the information your camera “saw” at the time when you pressed the shutter. Processing raw files takes some time and computing power but having them can be a real boon when you need to adjust the exposure, white balance and other things in your images during post-processing. The raw files are the only real #nofilter files out there.
This is by no means an exhaustive list of file formats out there, but everyone should at least know these few. All these formats keep evolving and different features such as bigger color depth and more metadata will be added to them, so the list will probably will be outdated in a few years. But for now we’re ready to get that picture of that dang hot dog.