What really is the difference between low resolution and high resolution digital images? I bet you know one is more quality then the other but most people don’t know the benefit of each one. Let’s break it down.
The word pixel means picture element. A pixel is normally in the form of a square and is the smallest element of the picture. A megapixel is one million pixels, so the higher pixels your image holds, the more detailed it is.
In the image below you can see how the picture is formed by millions of tiny little squares, or pixels.
Now that you know what pixels are, let’s move on to resolution.
Resolution refers to the number of pixels in an image. Resolution also refers to the pictures size. Let’s say you have a 3000×2000 pixel image. That means there are 3000 rows of pixels and there are 2000 rows (width and height). If you are into the mathematics, the said picture would be 6 million pixels, or 6 megapixels. You get that number by multiplying 3000 x 2000. Here’s the tricky part. Each pixel does not have a set size.
This is where it gets a little complicated. Since a digital image is not physical each pixel does not have a set size. So when you want to put a digital image on an physical object such as print, canvas, metal etc then those pixels get an actual dimension. In order to do that the print industry has come up with the measurement called PPI, or pixels per inch. A simple explanation of PPI is how many pixels can you fit in one inch. The more pixels per each inch, the better quality print you will get. Most print companies want 200-400 PPI to produce a good quality print. The math equation is PPI = width(pixels)/ width of image (inches); PPI = height(pixels)/ height of image (inches). Did that make you go cross eyed? Me too, so let’s put some actual numbers in there and simplify things a little bit.
The below image is 1400 x 931 or 1.3 megapixels.
Let’s say you want to print this picture in 4×6 inches. Here’s how the equation would be:
Width: 1400/6 = 233
Height: 993/4 = 248
So on the width there are 233 pixels per an inch, and height there are 248 pixels per inch. This will give you pretty good print quality. If you take the same image and you want a 16 x 20 size print then we can go through the same calculations:
Width: 1400/20 = 70
Height: 993/16 = 62
You can now see that the pixels are reducing quite a bit and odds are the picture quality will be poor. Since the pixels don’t have a certain size they will either expand or contract depending on the size of the print you want it to be at. So in order to print that particular picture at 16×20 the pixels have to expand making them more visible while the 4×6 has plenty of pixels so they will contract and become smaller giving you a much finer and better print quality.
Now that you know what pixels mean and how to calculate your image resolution it’s only right to cover DPI or dots per inch. This is a measurement of how finely spaced the droplets of ink can be in a print. This is not to be mixed up with PPI. This is why a 1440 DPI printer will not print a 1440 PPI quality picture, these are two different measurements.
Congratulations you figured out how resolution works, how pixels work and when someone tells you their picture is 300 DPI you can correct them and say dots per inch is actually a measurement of printer quality not picture quality, that is PPI (without sounding too much of a smartypants).
Now it’s time to understand why it’s good to have both high resolution files and low resolution files. High resolution files are good to have for the obvious reason, better print quality means you can print larger prints. Low resolution files on the other hand are often overlooked.When you open up a website the person designing it has gone through different lengths of making sure it loads up fast. If it doesn’t then it’s very likely you loose patience and leave before it loads. This is why we have low resolution images. They are a smaller file size and will in return load faster on the website. The mass communication websites such as social media has a way of compressing images you post. What that means in short, is that they automatically reduce the picture quality to create a smaller file. Unfortunately this will also ruin the picture quality and change the picture from a great picture to a poor picture. This is why it is so powerful to have the low resolution files so you can show the world the full quality of your image. You certainly don’t want to look a little distorted or with an odd skin tone since the colors are a little off. Most photographers strive to get things right out of camera in order not to have to edit the picture heavily. The same goes for posting a picture on the internet, we go through different lengths to edit the picture and make sure those colors pop and your skin looks just right for having Facebook ruin the picture. I hope this gave you a better understanding into resolution, pixels and why I give out both low resolution and high resolution images.
Most print companies will tell you if the print quality is too low. Unfortunately some will not. They will let you spend those $50 to get a 20×30 print that will look awful. I always make sure to use good print companies with good photo labs. I stay away from Walmart, Target, Walgreens etc as they almost always will not get the colors correctly.
Here are a few I’ve used and like: