Image Resolution: High Res vs Low Res

07 December 2017

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As designers, it’s easy for us to talk about industry terminology, which often means little to our customers (and can be misunderstood/contradictory within the industry too!) but we want to help. This post is intended as a primer for some of the jargon and common confusing areas of image resolution (or ‘res’ as us designers may say), specifically for print. We’ll stick to the basics to help you get the most out of your project.

Image resolution example

Why are designers always talking about image resolution?

Well, it’s because we want your project to be the best that it can be. It’s worth remembering that every piece of printed communication that you publish directly reflects your brand and its values to your customers and employees. Low image resolution (low res) in print looks unprofessional and no one wants to come across as being low on quality, am I right? So as much as it might seem like it’s just us picky designers with a bee in our bonnet about image resolution – trust us, we have your best intentions at heart!

What does image resolution really mean?

Resolution of an image refers to the amount of pixels or dots that make up the image. Digital images are made up of thousands of tiny blocks of colour, known as pixels and printed images are the same but with dots of ink. The number of pixels or dots in any given image determines how high (or low) the image’s resolution is – the more you have, the clearer and more detailed it is. Higher image resolution = Crisper … and the clearer the image, the better it will reproduce in print. Lower image resolution = Less detailed and blurry

Resolution is measured by Dots Per Inch (DPI) and Pixels Per Inch (PPI). They both describe the image resolution but they are different. DPI is the measurement used for printing, quantifying the number of ink dots in the printed document. PPI is the number of square pixels per inch of a digital screen. As a general rule, images for print need to be a minimum of 300 pixels per inch (PPI) when designing but, just as importantly, the physical dimensions of the image need to closely match the required output print size. So, if the intention is to print an image at 20cm x 30cm (roughly A4) but the image is only 4cm x 6cm then it doesn’t matter if the image is 300PPI, it’s still going to be too small to print at the required size. The difficulty is that physical image size trades-off against resolution – as one goes up the other goes down. For example, the 4cm x 6cm image would actually need to be 1500ppi to be of use for print reproduction at 20cm x 30cm. But the image looks good on my big screen? When it comes to displaying images on screen you need far less pixels than you do for printing. This is because the density of pixels on screen is far less than what is required for printing. For example; a typical monitor is 1920 by 1080 pixels in size so, to fill the monitor you only need an image that is 1920 by 1080 pixels in size. That’s about the same size image you need for a 16cm x 9cm at 300 ppi.

Image resolution diagram

How can I tell if my images are high enough resolution?

Here’s where it gets a bit tricky – it can be difficult to determine the image resolution without access to photo editing software such as Photoshop (we appreciate that most of our customers don’t have access to such software). However, depending on the system which you are using it may be possible to ‘right click’ on your image to view the image properties to determine the resolution. Also (and by no means fool-proof) it is possible to get a rough idea of the resolution of an image by looking at its actual file size. Generally speaking, the more pixels an image contains, the bigger the file will be. These are very rough approximations, just to give you an idea of expected file sizes (based on none compressed JPGs). If the file size is: Less than 200kb – probably only be suitable for use on screen 200kb-1mb – small thumbnail or inset 1mb-2mb – up to A5 3mb+ – up to A4 5mb+ – A3 or over   If you’re in any doubt, then send the image over to us – we can quickly check and let you know.

Myth Buster

All images are either high res or low res? It’s more helpful to think of image resolution as a scale from low to high rather than an either/or situation. It’s more about having images with an appropriate size and resolution in relation to their desired print output size.   Can’t you can ‘scale up’ an image? Like in the films when they zoom and enhance. No, unfortunately not. This is, at least for the time being, science fiction I’m afraid. If the pixels aren’t there to begin with, we can’t magically create them.   Is higher resolution always better? Generally speaking yes, up to a point where file size would make supplying and working with an image difficult.   Well, I hope that helped but if you have any questions just leave a comment below.

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