PDF - Portable Document Format
This file format was created by Adobe and with Adobe Reader (a free downloadable program) you can view any PDF. PDFs are a universal tool to share graphics with just about anyone and depending on how they were saved to begin with may still be editable in programs like Adobe Illustrator or with plug-ins like PitStop.
JPEG (JPG) - Joint Photographic Experts Group
Joint Photographic Experts Group - created the standard for this type of image file and named it after themselves. JPEGs compress a large amount of information into a smaller-sized file. In order to make the file size smaller, some details of the original image are lost. If you started with a vector image and save it as a JPEG, it is now a raster image. JPEGs are not great for text, line drawings, and most logos or graphics as they will look somewhat bitmapped or have a haze around them (noise); however, this is the only way to send larger images, such as full-page photos, to the printer and still have a manageable file. However, if you still want images to look good, make sure to save them with the Large or Maximum setting. These are also very suitable for web use.
EPS - Encapsulated PostScript
This is one of the most common vector type files. This type of file can be opened with Adobe Illustrator. EPSs are often used for logos, drawings, and text-heavy images.
TIFF (TIF) - Tagged Image File Format
Layered TIFFs are uncompressed files and therefore are large files containing a lot of detailed image data. In this format TIFFs allow for flexibility of color and content. Designers will also use TIFFs when files need to be compressed, by flattening the layers, but this is done in a way that is lossless in detail as opposed to JPEGs.
GIF - Graphic Interchange Format
Most often when you think of GIFs these days, you think of animated shorts used on cell phones or social media. GIFs compress images, differently than JPEGs do, but they have an extremely limited color range (up to 256) which makes them suitable for web use and not for printing.
PNG - Portable Network Graphic
This type of image was created to compete with GIFs. It allows for a fuller range of color (up to 16 million) and has great compression without loss of quality. However, it too is used exclusively for the web and not for print projects. These differ from JPEGs in that they do not have to have a background, which makes them great for icons or placing logos on different colored areas of a web page.
PSD - PhotoShop Document
This is an open-layer document created using Adobe PhotoShop. While it is a great design tool, it is not usable in print projects due to the size of the files and tendency for layers to not “rip” or rasterize properly for the press. In order to use PSD files in print, they must first be converted to flattened JPEGs or non-layered TIFFs. If you submit an open-layer file, you MUST also submit all files placed inside the document and ALL fonts used.
AI - Adobe Illustrator files
These are native Adobe Illustrator files and are where you create vector files. Once you have finished creating your file in Illustrator, you would save it as either an EPS or a PDF to use in your printed piece. If you submit an open layer file, you MUST also submit all files placed inside the document and ALL fonts used.
SVG - Scalable Vector Graphics
This type of file was created to address the need for a versatile, scalable, vector format for online use. Generally, SVGs are used for logos and on responsive website builds where a large logo can be seen everywhere from a widescreen high-def monitor down to a small cellphone screen.
RAW - Raw Images
Raw images usually come from a digital camera. They are raw because they haven’t been processed or edited in any way. Each camera manufacturer generally has its own raw format and you either need proprietary software or a program such as Photoshop to work with these files. These files are extremely large because they contain a large amount of uncompressed data.
BMP - Bitmap Image File
Generally TIFFs are preferred, although these are used for scans and archival copies. Bitmaps are rarely used anymore.
What Is a Raster Image
Raster images — think of photographs — are composed of individual pixels. Raster images are capable of creating complex images with layers of colors, including gradients. All the images you see online are raster images, with the exception of SVGs but that is a whole other topic. Because online images are raster, you can’t take one and blow it up to an 8x10 photo - it will look blurry and bitmapped. You can only decrease the size of a raster image, not increase it. Most web quality graphics are 72 pixels per inch (ppi) while most printers will request that graphics be 300 ppi and set to the size that they will be printed. The image above shows what happens when you take the smaller image of the leaf and try to blow it up to a larger size when it has already been rasterized.
What Is A Vector Image
Vector graphics are composed of editable paths, each with a mathematical formula. Vector images are scalable and do not lose their sharpness no matter what size you change them to - postage stamp to billboard and back again. While vectors can be used to imitate photos, they are better suited for solid colors and shapes where each area has its own color. Vectors cannot achieve gradients, shadows, or the shading that raster images are able to. However, because they can be scaled infinitely, they are well suited for logos, signage, and for promotional items such as embroidery. The image above shows the larger leaf blown up in vector format before it was rasterized for the web. You can clearly see the difference in clarity compared to the raster image in the sample above.