If you often use digital files, you frequently come across various terms designating certain things about the digital file. While many of these terms communicate important information, not everybody understands what these terms mean. In this article, we will learn about terms that designate file time, printing size, and resolution. Hopefully, by the end of this article you will have a better understanding of the files offered for sale or free download in various parts of the internet and will be able to make more confident choices. 

Image file types

A file description generally includes the file's type. There are various types of digital files, and different types of files are used for different things. Some file types, for instance, are used for word processing. Others are only for music, and still others for movies. The main file types you will encounter in dealing with images are JPEG, PDF, PNG, and ZIP. 

JPEG

A JPEG is an image file. Most digital photos are JPEGs. A JPEG has only one page. They can be printed, but printing will need to be set up (sizing, etc.) If you create an image in image editing software and use layers, all the layers will be merged in a JPEG. The image will look the same, but it will not be possible to edit individual layers by themselves. 

PDF

The name PDF stands for portable document format. It really is a kind of container file. Unlike a JPEG, a PDF can have separate layers that can be edited separately. Unlike a word processing document, it retains visual elements like fonts, etc., which might be lost when transferring a word processing document from one computer to another. Various kinds of files can be made into pdfs, and a pdf can have multiple pages. It is a good way to combine multiple documents for printing. 

PNG

A PNG file is similar to a JPEG file in that it is a flat image file. The main differences with a png is that it can have transparent parts to it. That is, it doesn’t have to have a white background. Clipart files are generally pngs, because they are images without background.  In my experience, PNGs tend to be larger files, as well.  

Zip file

A zip file combines several other files into a single file. Your device probably has software on it to open zip files. Generally, all you have to do is click on the file. People use zip files because they allow multiple files to be treated as one and allow for some compression, or reduction in file size.  If you download multiple files at once, you might download them as a Zip file.  You probably also download Zip files if you download photos from a cloud storage service. 

Other formats: 

Raw: This format is used by professional photographers. If you have a "pro" setting on your phone camera, pictures you take in that setting might be in this format. Not all image editors can handle this format. 

SVG or Vector: This is an entirely different type of image format. While most image formats are composed of tiny dots called pixels, vector graphics are completely different. Since they are stored as descriptions, not pixels, they can be scaled to different sizes without loss of quality. 

Printing sizes

US Letter

This is the most common paper size in the United States. It is 8 1/2 by 11 inches.  

A4 

This is a common paper size in Europe. It is slightly longer and narrower than US Letter, 8.3 by 11.7 inches. If you are in the United States, you may be able to buy A4 paper online. This size may be better for bookbinding or junk journal making as it is longer, making wider pages. 

Orientation

Documents can also be categorized by their orientation, whether they are wider than they are tall or taller than they are wide. Documents that are taller than they are wide are portrait orientation. Documents that are wider than they are tall are landscape orientation. 

Resolution

What is DPI?

The term DPI means “dots per inch.” The dots referred to are also called pixels. These are the small dots that make up a printed or digital image. The more dots or pixels per inch, the higher the image’s quality, that is, the sharper the details in the image. An image can only have a dpi if it also has an intended printing size. Otherwise, its size is simply a number of pixels in width, a number of pixels in length. 

What does resolution have to do with printing size? 

An image might have a number of resolutions depending on the intended printing size. The images I sell are usually intended to be printed out at either US Letter size or A4 size. However, if you were to print one of my image out bigger, say twice the intended printing size, the resolution would be lower because you would be spreading the same number of pixels out over a larger area. Most high quality images are 300 dpi, but, if printed out larger than the intended printing size, would have a different resolution.

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