Have you ever tried to use a photo you found online in a presentation or document and it looks blurry? Or tried to order a print of an image and the website tells you the file isn’t high enough quality?
Understanding image resolution can help you avoid those problems.
(Lookout, we’re going to get a bit technical up in here today!)
It boils down to this: photographs are constructed using a fixed number of colored pixels. Photos are measured in pixels per inch (ppi) which indicates how many pixels there are, indicating the level of detail that’s contained within them. The more ppi your image contains, the higher the quality of the digital image.
For example: a 1-inch by 1-inch image at 300ppi equals 300 individual squares of color. Likewise, an 18 by 24-inch image at 300ppi contains 129,600 squares of color. Keep in mind that more pixels means a much bigger file size.
Now let’s say you want to take that 1-inch image and print it as a 3-inch square picture (triple the size). Since there is only a fixed number of pixels, the computer has to take its best guess as to what colors should fill in the gaps. It’s called interpolation, and it’s what causes an image to appear blurry when it’s enlarged. The computer really has no way of knowing what colors to fill in the gaps with.
So what’s a suitable resolution for an image? Well, it depends on how you’re using it.
The pixel density determines what the image is suitable for. If you’re using an image on a website or social media, you need a relatively low pixel density – 72 ppi. The goal for screens, websites, and social media is smaller file sizes with less color information that can load quickly.
But if you want to print an image, you need a lot more pixel density. Ideally you want 300 ppi, which is much higher than a screen resolution. For printing, a bigger file size with more color information works better.
Which is why taking a small, web-sized image you find online doesn’t work when you try to make it bigger or use it in a print project.
But how do you tell what resolution an image is?
Hovering over the image file in your file explorer should give you the pixel dimensions of the image. But here’s another quick trick…check out the size of the file. If a picture is measured in kb, it’s not a high-resolution image. Period.
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