“A picture is worth a thousand words” is the obligatory idiom to invoke when discussing the
visual medium. It’s of no surprise either because it is, in fact, true. Human beings have been
using visuals to create long lasting messages since the time they dwelled in caves. History,
in a sense, started off with pictures. Today, for those working in the visual industry, images
can be considered their most important mode of communication; their alphabet. And like
the alphabet, they come in many characters, and just as vowels are used more often than
consonants, so too there are image formats that can be spotted more frequently than
others in the wild. In this post, we’d like to go over, as a refresher, the image file formats
designers tend to use, and when it is suitable to use each one of them.
To start off with, it’s important to note that images fall into two formats, raster and vector.
Raster images can be thought of as a grid of dots similar to the graph paper used in high
school math classes. Each dot is a pixel that is assigned in some cases only a color value,
and in others color and transparency (more on that in the categoriztions). Raster images are
fixed in resolution. When you pull at the corners and stretch your raster image, you are
actually torturously stretching the pixels themselves stripping them of their gleam and
ending up with a blurry, ‘pixellated’ image. Raster images are most commonly found in
digital artwork, photos, and web graphics.
There are two primary features when it comes to raster images: their color mode, and the
algorithms used to save them.
CMYK which stands for Cyan Magenta Yellow and Key is the format that is ideal for printing.
The colors of made of the the four ink types the name implicates, key being black here.
RBG (Red, Green, Blue), on the other hand is based on light, namely the light mixed and
used on monitors to produce all the colors we see. This format is ideal for anything that is to
be shown on a screen.
Images can be saved using many different formats and optimal compression has long been
the mission of many a hopeful computer science graduate and/or entrepreneur (see HBO’s
Silicon Valley). Lossless conversions preserve and reproduce all the information that was in
the original image. Lossless formats can be compressed but not as much as lossy formats,
which tend to discard just enough information to be able to approximate what the original
image looks like.
JPEG, the most common and most widely used image format is of the lossy clan.
Developed by a technical team that knighted itself the Joint Photographic Experts Group,
JPEG images can be compressed all the way to nearly unrecognizable pixellation. This
freedom to compress, or keep optimized, makes JPEG ideal for both online and print
GIF, which stands for Graphics Interchange Format is the most common format you will find
when it comes to memes, Tumblr blogs, and any idea that can be condensed into a few
seconds of movement. GIFs are lossless and have an alpha channel for transparency, but
offer a number of options when it comes to compression. They are ideal for short
animations with small sizes and pronounciation wars.
PNG (Portable Network Graphics) is fast moving in on, and looking to overtake JPEG as the
most common image file format. With a variable transparency channel, millions of colors,
and high quality compression, PNG is the go to format for web graphics. Just be wary when
working with photos as PNGs can bloat and grow in size quickly.
Tiff, Tagged Image File Format, is a lossless format that lives up to the lossless title. The
original image data is always maintained no matter how often it’s recycled, tumbled, saved,
re-saved, deleted, and recovered. This gritty nature makes TIFFs ideal for photography and
desktop publishing but not so suitable for the web - unless pre-broadband wait times are
the nostalgia you are seeking.
Raw images, as their name suggests, are images that come free of any manipulation and
compression. Typically the output of digital cameras and sensors, raw images contain both
processed and unprocessed information giving the user a high quality image with
complete creative freedom to manipulate to their heart’s desire.
No image file format discussion would be complete without the honorable mention: PSD.
Short for Photoshop Document, PSD files are the industry standard that have capabilities
that extend far beyond other formats. They contain within them multiple layers and a
plethora of adjustment information. Not stopping there, PSD files can also contain within
them vector layers making them fit for both the raster and vector image category.
Unlike raster images, vector images are composed of equations. Equations that store
information about every dot, line and shape in the image. Vector images are resolution
independent and will retain their crisp, clean look as both a logo on a business card and a
poster on a building! This flexibility makes vector images ideal for illustrative work of any
PDF, yet another creation of Adobe stands for Portable Document Format. The intention
behind its creation was a universal format that could display graphically rich information on
any and every platform. It would not be an understatement to say that they have achieved
just that. Adobe Acrobat Reader, a free software package, is the only requirement necessary
to view documents of this kind. The vector graphics engine behind this format can display
both raster and vector images and even offers limited editing capabilities to boot.
EPS (Encapsulated Postscript) is very similar to the PDF format with the addition of being
supported by applications outside of the Adobe universe such as Corel Draw and Quark.
Though this format supports raster images, it is primarily intended for the vector format.
Just as the PSD format is the industry standard for raster images, AI (Adobe Illustrator
Document) is the preferred format for vectors. Adobe Illustrator allows for exporting in both
the EPS and PDF format. A very powerful tool that belongs in every designers arsenal,
Illustrator is primarily used in creating logos, illustrations, and type.
This list is by no means exhaustive (taking a look at the wikipedia page for image file
formats is enough to cause diziness) but does cover the most common formats used in the
world of design as we know it today. New formats will undoubtedly pop up in the future but
unless they deliver some astounding new feature or display some jaw-dropping
compression algorithm, it will be difficult to dethrone the standard ones we use today.