Clearing Up the Mystery of Image Resolution
What is Resolution?
Resolution is basically the number of pixels or dots an image has in a given space. Pixels and dots are basically the same thing; except dots are used for print and pixels are used for digital media. The higher the resolution of an image, the more dots it has. I’m American so I’ll be using inches for this article, but the same principles apply for centimeters. A 300 DPI images has 300 Dots Per Inch while a 72 PPI image only has 72 Pixels Per Inch.
A 100 DPI image and a 300 DPI image can both have the same dimensions. (This is where it gets confusing.) You can have a 1”x1” image with 100 DPI, which is 100 dots total. Or you can have a 1”x1” image with 300 DPI, which is 300 dots total. As you can imagine, the image with the higher resolution will generally look sharper.
Why not use high resolution images all the time?
The reason that high resolution images are not used everywhere is because they are very large. You might hear web developers refer to this as “heavy”. There is a constant battle going on with the internet between quality and quantity. Developers want their websites to look amazing, but they also have to load quickly and efficiently. This process is called optimization, and is a process that is always being innovated and improved. The resolution you use depends mainly on the type of media your image will be used for. Most computer monitors only have a resolution of 72 DPI so using a resolution higher than that is a waste of loading time because you can’t see the difference with your eye.
The same is true for video. HDTV is 96 DPI so any video with a higher resolution is wasting valuable space on your band width or DVD. When it comes to printed media, your eye can pick up a lot more detail. Most printing companies like to have their images at least 300 DPI.
However, when it comes to larger printed media such as posters and banners you can get away with a lower resolution because these objects are viewed from a distance. This is important to note because large print files can take a long time to work with and save. They can really make your computer work so shaving off a few pixels can really cut down on the “weight” of the file and save some time.
That is the basics of resolution in a nut shell. I have prepared this flow chart to help you when deciding what resolution you should request from your artist.