What’s dpi? A Beginners Guide


At Vintage Photo Lab we love scanning our customer’s old photos, ensuring they are preserved digitally for generations to come. And whilst we are experts in this particular field, we realise that some of our customers want to know more, particularly when it comes to ‘dpi’. Here’s our beginner’s guide, a quick look at all things dotty.

What is dpi?

‘Dpi’ stands for ‘dots per inch’ It is a way to describe how much picture information is held in one square inch of a print or digital photo. Each one of these dots within the square inch can be a different shade or colour, depending on the overall photo. Close up they’ll appear as blocks of colour, but from a distance, your eye blends these together to form the overall image.

Dpi is scored in numbers, 72 dpi, 300 dpi, 600 and beyond. The bigger the number, the greater the picture information held in that particular square inch. The greater the information, the clearer the picture, the bigger and better any future prints or projections will be.

A Bit of History

So why are they measured in inches, not cm? The term dpi has its origins in historical newspaper printing. Photos in newspapers were originally printed in black ink, produced out of a series of dots of differing sizes. These dots were sized and scaled in ‘lines of dots per inch’. Again, when viewed from a distance the eye would blend these dots to form the image.

Whilst we now live in the digital age, the principal of scaling dots used in printing to form an image remains the same, hence we still use the similar term – ‘dots per inch’, or dpi.

What is Low, Standard & High Resolution?

Scans are sometimes referred to as Low, Standard & High Resolution, or ‘Low Res’, ‘Hi-Res’ etc. for short. It is a more general way to describe the dpi of a particular scanned photo, 72 dpi would typically be called ‘Low Res’, and 600 dpi would be called ‘High Res’.

Why Do We Have Different Scans Sizes?

When looking to get your photographs digitised you don’t always need to get the highest resolution available. How you want to use the final scanned image will greatly determine the quality of the scan you have made. Let’s look at some different scan sizes and their pros and cons:

 – 72 dpi

A low-resolution scan. A scan at 72 dpi will retain the look of the original but lack the fine detail. If you were to print a photo the same size, you would potentially notice a drop in quality they could look slightly blurry, lines not as sharp. Scans at this size are good for quick and easy online sharing.

A 6×4 in print scanned at 72 dpi will take up approximately 150KB of memory space.

 – 300 dpi,

A standard resolution scan. A scan at 300 dpi will retain the visible information from your photo. if you were to print a photo from the scan, you wouldn’t lose any quality printing the same size or slightly larger. Great for showing on TV and computer screens. It’s ideal for your photo books up to A4 size.

A 6×4 in print scanned at 300 dpi will take up approximately 2000KB, or 2MB of memory space.

 – 600 dpi,

A high-resolution scan. A Scan at 600 dpi will produce a large digital file. It will capture the fine detail in the photo, details not obviously visible without a magnifying glass. You can make print enlargements up 5 times the original size without losing quality. To capture such fine detail these scans take longer and use more memory space. Excellent for projecting large scale, the right scan size for making larger photo books.

A 6×4 in print scanned at 600 dpi will take up approximately 8000KB, or 8MB of memory space.

All I Can See is Dots

So why get your old photographs scanned? There are so many reasons why you’d want to do this, to create your own family book, to share memories with families and friends, ultimately the best reason to scan and digitise your old photos is to protect these memories for generations to come.

A photograph is an incredible thing, born out of Victorian ingenuity, skill and chemistry, but they can be fragile. Once digitised they can be shared, saved, published online, the possibilities are endless. They’re future proofed.

If you’d like to know more about scanning or would like a free trial of our services, please get in touch we’d love to hear from you.

Happy scanning & remember to watch out for the dots!


Vintage Photo Lab