What is image resolution | DPI or PPI



But what about the confusion surrounding the totally different, important mis-use of the other ppi — pixels per inch — and dpi, dots per inch? Preparing an image for web or print can lead to confusion, especially if you are not trained in design, photography or print.



Using an unsuitable image resolution is a common error. Seeing a blurred or fuzzy image on screen or in a brochure is a poor representation of your company brand. By understanding the basics of setting up your image properly for where it will be used will avoid these issues.

First you need to understand that pixels refer to the coloured squares that make up an image and hold the detail. The lower the number of pixels, the less detail in the image. On screen or digital image resolution is fixed by your electronic device, but we are often told that 72 pixels per inch (ppi) is best. What you really should be told is that it does not matter if you upload an image to a website at 72 ppi (low resolution) or 300 ppi (high resolution) because the visual output is still the same. Ultimately, the size image you upload to web is down to personal preference; for example if you want people to be able to download your images at high quality or not, or if you are limited to uploading a specific file size.



Dpi is often confused with ppi. This refers to dots per inch, which is only a printer’s reference to physical dots of ink that make up an image. Images for print purpose are usually requested at 300 ppi in high resolution to offer a crisp, unspoilt visual with smooth colour on paper. Anything low in pixel range will result in a poor quality ‘pixelated’ finish up close.

When it comes to print, high resolution images are needed in order to look best. It is possible to change image resolution using an editing tool such as Photoshop, however the original physical size of the image needs to be looked at. Is it physically big enough to work for print at the scale you want it, or does the image need a resample?

The only time a high-resolution image may not be required is when printing extra-large, super scale print such as billboards. Your printer will often request the files are scaled down because the target audience will be standing far away in a place where the image will appear to look smooth. However, up close the square pixels will be more visible. There is a lot of maths involved when it comes to dpi, but that is more for the printer to worry about rather than the designer.

Overall, you only need to think about ppi rather than dpi for any image in print or online. If you are still confused it is worth clarifying with the person requesting the image size whether they really mean ppi if they ask for something in dpi. Sadly, dpi is so often mis-used — even by big brands.

Image quality can be changed by resizing or resampling. However, it should be done by someone who understands the image purpose and requirements so as the maths can be properly considered.

For more insight, learn what the rule of thirds is.

For any further advice or graphic design queries contact Stone Junction on 01785 225 416 or e-mail sayhello@stonejunction.co.uk.

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