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Dear PC Doctor:
I always thought all image file types were basically the same – but I recently saved a document as both a jpg and a PDF, and when I printed the jpg, it was not as crisp and nice as when I printed the PDF. Same printer, same original file. What’s happening? Is there a real difference between types of image files, or am I imagining it?
Signed, Fuzzy
Dear Fuzzy:
There are lots of different kinds of image files. I’ll bet you’ve heard of GIFs, PNGs, JPGs, and TIFFs. There are also PDFs, which are used for more than just pictures.
GIF is short for Graphics Interchange Format. GIF is a file format for storing images (limited to 256 colors.) It uses a lossless compression method which makes for higher quality output. The GIF format also is used for looped animations, like the kind you often see on social media sites.
PNG stands for Portable Network Graphics, and was created as a more powerful alternative to the GIF file format. PNGs are not restricted to the 256 color limitation of GIF files and have better compression. A PNG file can be saved with a transparent background which allows you to place your image on top of another image without an outlining white box. The color of the background will show around the image.
JPG stands for Joint Photographic Experts Group. JPGs compress image data by reducing sections of images to blocks of pixels or "tiles." JPGs are best for small image files for web sites or email. When JPGs are compressed and saved, some quality of the image is lost. Because of this, JPGs are not the best way to store images – Every time you save a JPG, some of the quality is reduced. Despite the quality issue, JPGs are very useful in that they are accepted in almost every app and word program. Tools like Publisher and Canva don’t allow you to work with PNGs and PDFs.
TIFF means Tagged Image File Format, and is used for high resolution images. TIFF files can be saved in a variety of color formats and in various forms of compression. TIFFs are often used for professional photography.
PDF means Portable Document Format. The PDF format was developed by Adobe for distributing compact documents that will look the same no matter where you view them, and on any platform. Everyone you send a PDF to will see the same thing, with all the same formatting. PDFs are also used for online forms.
You can read more about file formats at: GCFlearnfree.org, gizmodo.com, http://guides.lib.umich.edu, lifewire.com, and many other sites.
Until next time,
Happy Computing!
PC Doctor
Editor's Note: Questions should be directed to PC Doctor, care of the Athol Public Library, info@athollibrary.org or Athol Public Library, 568 Main St., Athol, Mass. 01331, or dropped off at the library.
Posted: to Athol Library News on Fri, May 25, 2018
Updated: Fri, May 25, 2018