Image size, or What’s a DPI

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Several things affect how big a file is, i.e. how much space it takes up on the hard drive, in kb or mb (kilobytes or megabytes):

1. Resolution, measured in dpi or dots per inch. A picture that is 300 dpi will be bigger than one that is 72 or 96. 300dpi is the minimum for something to print nicely. All that a monitor will display is 96 dpi so no picture ever needs to have a higher dpi than 96.

72-96 is low resolution.

300 and up are high resolution.

2. Physical size on the screen (dimensions measured in pixels). An image that practically fills your monitor/screen space (say 1000×700 pixels) will be bigger (in kb) than if you make that same picture 500×350 or whatever.

3. How many colors in the image.  An image with a lot of colors will be bigger in kb than an image with fewer colors. So, if you have a very colorful product, the best background would be something solid and in a neutral tone. Changing the text in the image below from red to white added 10 kb to the image size.

Don’t forget that there are still people out there who have smaller monitors. And a lot of us don’t maximize the windows on our computers. Right now I can see Firefox (which I prefer to Internet Explorer) and Dreamweaver (my web design program) and Eudora (my mail program) and my favorite image editing program, Fireworks.

Having multiple windows visible reminds me what I need to do.   So even though I have a 25″, high definition monitor, I don’t like websites with giant pictures where I have to maximize the window to see the whole page.

Of course, most of my clients are trying to sell products online. So I’m always thinking of how best to do that. And the hardest thing for clients (including my daughter) to remember is that a website should be designed for the buyer. It’s all about making it easy for them to find what they want quickly. Naturally, the website must be visually appealing, but the main person to please is your customer, not you.

More on that later.