Are you confusing a JPEG with a GIF? How can you decide if you should pick a BMP or a TIF? Which image format is the best choice for a document, website, or presentation? How do you sort out the alphabet soup of graphic acronyms? Including proprietary file formats, there are hundreds of different image file types although only a few dozen are widely supported by the programs on your desktop. Let’s look at your options to get the results you need.
There are two primary categories to describe the techniques used to build a graphic: raster or vector. A raster image is also known as a bitmap and is created from rows of small dots of color called pixels (“picture elements”) or “bits.” The big disadvantage is they are a fixed size. If you try to alter the size of a raster graphic it gets the “jaggies” or those rough, stair step edges on a graphic. Most commonly available images are a bitmap or raster format.
Vector image formats contain a geometric description which can be created smoothly at any desired display size. Examples of vector graphic files are EPS (Adobe Illustrator) and CDR (CorelDRAW). When available, vector graphics are generally best for printing because they can be easily re-sized without the “jaggies” but many formats are not widely supported by desktop programs.
In addition to the specific graphic file formats detailed below, the resolution of an image also impacts the appearance. Image resolution is described by DPI (dots per inch), a graphic measurement. For instance, most web graphics are 72 to 96 DPI which is fine for screen viewing and even PowerPoint presentations but lousy for printing. This is why most Internet images are blurry when inserted into a document. Ideally, a graphic you want to print should be created and edited with a minimum resolution of 300 DPI.
Do you have huge PowerPoint files? The biggest cause of presentation bloat are photos with large dimensions and a high resolution. Did you know that even if you re-size an image to a much smaller scale, PowerPoint and Word still store the photo in its original size? Fortunately, Microsoft Office programs include the option to compress images to reduce the size and remove any cropped areas. Even better is to modify your photos and other images first using an image editing program such as Photoshop or Photoshop Elements which can significantly reduce the size of the files.
Here’s a look at the pros and cons of some of the most common graphic file formats. FYI-each of these are raster images.
The JPEG, GIF, and PNG file formats are all perfect for graphics on the Internet. They are usually not recommended for printing since these are typically much lower resolution files and cannot be enlarged without losing design detail. It is becoming common, however, for a graphic designer to create a company logo or other frequently used image as a high resolution JPEG to provide an all-purpose graphic file which can be inserted into web pages, presentations, and printed documents.
If you don’t have access to the original images or editing programs and are limited to graphics created by someone else, take comfort to know that over 20 different graphic formats, including each of the image types described above, can be inserted into Microsoft Word, Excel, PowerPoint, Publisher, and even Outlook. Just choose the Insert tab or menu and then select Pictures (From File) to see your options.
Working with graphics should now be much clearer and simpler with these time-saving tips.
By Dawn Bjork, MCT, The Software Pro®
Microsoft Certified Trainer, Technology Speaker, Software Consultant