I was trying to explain resolution to someone the other day when I realized that we think in these terms every day. However, it can be a complex issue for someone who has never had to work with image resolution before. It is becoming important for more people to understand a little about what makes an image look clear vs. blurry when submitted to a blog, Facebook post or to a photo gallery. This is not an attempt to explain all of the details of resolution — just the basics to get you on your way to getting quality images up on the web.
The first step is a pixel. Pixels are the subatomic particles of images. They are the smallest particle of an image that can be manipulated. All images are made up of individual pixels. The amount of them determines how large an image is. And, the more of them there are the more detail an image can have. Dots per inch (DPI) and pixels per inch (PPI) can be used interchangeably in this example.
The next thing to remember is that web display resolution is 72 pixels per inch. Most services will give you dimensions as pixels and will be formatted width by height. For example Facebook profile photos are limited to 200×600 pixels. Because there are 72 pixels per inch in web display we can divide 200 by 72 and come up with 2.77 inches wide. So as long as you have an image that is 72 pixels per inch and at least 2.77 inches wide you have something that will look as intended on your profile picture. If you don’t like doing the math you can also visit a site like tiporama.com to help figure out what you need.
Another thing to remember is that some places on the internet will downsize a photo for you. If you submit something that is too large. They will have something on the website behind the scenes that will make the image smaller to fit their criteria. Pictures that are smaller in size will not look very good if enlarged. By enlarging a smaller picture, all that happens is the pixels get larger and more distorted. But pictures that are larger can be made smaller and not hurt the image.
Lastly, if you are unsure of what you need you can post it and see if it will work. If it doesn’t look good you can always remove it and try again. It is better to start large and work down than to start small and try to work up.