12 Sep Image Resolution Explained
At one point or another, when supplying images to your designer, you’ve probably had them ask. “Can you please send over a High Resolution version?”
If you haven’t been asked this yet, you most likely will, so brace yourself.
So, what’s a “High Resolution Version” and why do pesky designers keep on asking for them?
Let’s start off by talking about Image resolution, and to keep it simple we’ll use “pixels” (px) as the form of measurement. What’s a pixel you ask? A pixel is a small square shape which has a colour value assigned to it. An image is made up of many differently coloured pixels which when placed next to each other, form the colour and tonal values of the image.
In this image sample you can clearly see the pixels that make up the image. As you zoom in on an image the pixels get bigger.
Due to their hard edge shape, pixels can be easily seen in an image that is Low Resolution. Low Resolution refers to the number of pixels that are being used to form an image. The number of pixels in an image is calculated by the formula, Pixels per Square Inch (PPI).
The higher or lower PPI an image has determines whether it is a high or low resolution image.
An image that is 100mm x 100mm with a resolution of 72 ppi is a lower quality image than one that is 100mm x 100mm with a resolution of 300ppi. Increasing or decreasing the size of your image will have a direct affect on the resolution. For example, if you increase the size of the image that is 100mm x 100mm with a resolution of 300ppi, to 200mm x 200mm your resolution will fall to 150PPI making it unsuitable for commercial printing. – This is why you can’t grab images off the internet and supply them to a designer for printing a brochure.
Standard Online Web images are 72ppi. Online images are restricted to viewing via screens and therefore only need to have enough resolution to display well based on your viewing screen.
So why does my designer ask for higher resolution images when we want to print a brochure?
When printing a brochure, the resolution needs to be 300ppi due to the extra image detail that can be seen when printed.
To work out if your images are suitable for printing, use this guide.
- Windows: Right-click the image > Properties > Details Tab > Horizontal/Vertical Resolution
Mac: Open the image in Preview > Tools Menu > Show Inspector > Image DPI
- Check that it is at 300 PPI/DPI.
- Take the pixel resolution components and divide them by the PPI to see how many inches wide the final version will print.
- The result will tell you if your image is suitable for Printing at the size needed.
Some general guidelines are, 72PPI for Digital use images and 300ppi for print use images, but remember that these need to be at the actual size that the image will be reproduced. No point supplying a business card sized image at 300 dpi if you want it printed onto a large poster. As you stretch the image into it’s larger size you will make the square pixels larger, and the image will end up pixelated.
Zooming in on an image will reveal that it is actually composed of square pixels. The more you zoom into an image the more the pixels are defined. Pictures 2 & 3 are considered “pixelated,” as you can clearly see each individual square.
I hope this short explaination hasn’t confused you further. If you’re still unsure about the quality and suitability of your images, forward everything you have to your designer and ask them to sort it. They’d be more than happy to have the option of choosing the right image for you. Problem solved.