We live in a high definition world. In fact, we’ve reached ultra high definition from what we watch on TV to the pictures we take. Needless to say, resolution plays a major role in image quality and clarity, but what exactly factors into resolution? After all, we’ve come a long, long way from our 4:3 fullscreen, 420p days.
It all starts with DPI (dots per inch) and PPI (pixels per inch).
Even though both terms refer to resolution and image clarity, they’re not quite the same thing, yet they seem to be tossed around interchangeably. So let’s shed some clarity to this issue.
PPI (Pixels Per Inch)
You’ve probably know about screen pixels and that more pixels give better image clarity and so on. Sound familiar, right? But do you actually know what a pixel stands for? It means “picture element” and it relates the the smallest physical element of a digital display that the human eye can see.
So, if you think of it in those terms, it makes sense that TVs with more, smaller pixels have better image quality. But here’s where it gets tricky.
PPI in reference to pixels, doesn’t actually matter like you think it would because that PPI number of whatever digital display you’re looking at is already set. For example, most LCD monitors are around 67-130 PPI. You can’t just adjust that to that number, it’s a fixed amount.
As a result, PPI and its image clarity really comes into effect only when someone prints an image from a digital format. PPI is a way to adjust the physical size of an image, not the resolution of the printout. The larger the pixels (aka the lower the PPI), the lower the image quality due to the bigger, more visible pixels.
DPI (Dots Per Inch)
Typically speaking, DPI refers to the number of physical dots on a printed image. But, let’s get a bit more technical for a moment.
When an image is printed, the printer doesn’t reproduce an image by tilting pixel squares directly on top of one another. Instead, tiny dots are printed and within these dots is a mix of the four main colors (cyan, magenta, yellow and key). Together, this color combination creates a range of hues and in between the space of these dots, even if it’s indiscernible to the human eye, is what DPI measures – their overall density.
Why does this all matter? Because the higher the DPI, the better the image, in both tone and overall color. To keep things in perspective, 150 DPI is generally seen as the minimum standard for high quality photography reproduction in most printed books and magazines. Newspapers come in even lower, around 85 DPI, which is why you can see actual individual printed dots on your paper. Billboards can even be printed as low as 45 DPI, but because they’re viewed so quickly and from so far away, the human eye can’t discern the dots.
As you can see, there’s a lot of factors that fall into place when talking about resolution, and when it comes to digitizing your old media it can become a popular topic. How will digitizing affect resolution? Will it even affect it? Hopefully now, you’ve got a little more clarity on the subject and what it means for preserving and enjoying all your aging memories.