There are many numbers in life that are considered a measure of quality. Most are confusing to some extent, as they are often twisted by marketers into selling points. Lets take effort for example – it’s no longer acceptable to give 100%, it’s 110% minimum these days!

How Digital Made The Dpi Go Up

Remember when we invented the digital camera? In the first instance we were just pleased to have them. A camera that doesn’t need film? Brilliant! No more chemicals, no more waiting two weeks to see your pictures? Absolutely amazing. And then the advertising guys stepped up. Our camera is so great – (they said) that it shoots at a VGA resolution. That’s exactly what you get on the screen! Perfect we thought. WRONG! What you need, say the marketers, is something better. A 1 Mega Pixel camera is what you need. Mega! That’s got to be better than that old fashioned what you see is what you get resolution. Next is was 2 mega pixels, then 3. Time went on and so the numbers went up and up and up. Fast forward to today and we’re in a situation where you can shoot a 41 mega pixel picture with your telephone. I’m not sure what these guys are going to come up with next year, but let’s just assume it will be better. Or at least the numbers will be bigger.

Put that on my screen

So that’s viewing things on screen covered really. The point I’m making is that when viewing things on a screen, any captured pixels you’ve got are basically wasted. Sure if you zoom in you get more quality, but the vast majority of images are left just as they are. Now pixels on a screen are getting more dense, more closely packed together. Back in the old days of the Classic OS, Mac users used 72dpi (dots per inch) for work on screen. But with the advent of the iPhone and your Samsung Galaxy that has ‘doubled’ up to 150dpi+. So for screens, resolutions need to be bigger and better, but compared to printed photos these images are tiny.

The Printed Page

When we get to the printed page these numbers really start to rise. Typically when talking about images printers will ask for a 300dpi image. This is not just because our machines are capable of printing at that density, but because lower dpi counts result in ‘blocky’ or low resolution images. Printed work is a lot sharper and constant than your typical glarey screen- even the most modern displays have some amount of blurring due to the way the pixels are illuminated. But the printed page is not at all forgiving, even a 200dpi image that looks amazing on your LCD display will look blocky and undefined under the scrutiny of print. Text is even more unforgiving, it’s smooth curves make low resolution output a big no no. The best way to keep your text looking smooth is by producing your work in a PDF format. As long as you remember to embed your fonts you should be golden. PDF files combine vector and raster data, which means any text or vector work will be reproduced at the highest resolution possible.

The Art of Perception.

Now stand back- here comes the next revelation. Big posters require a smaller dpi. It sounds crazy, but it’s true – for poster work you don’t need to be quite so picky about your high resolution pictures. It certainly is true that on close inspection low resolution pictures will appear blurry, but how often do you get up close and personal to an An A1 poster? Posters are generally perceived from a fair distance, which means we’re happy to accept things being less than pin sharp. Check out a billboard next time your walking past, you’ll be amazed at how low quality the half toning on images can appear. Here at Print Colchester we recommend 200dpi images for large format poster printing, this kind of resolution should keep file sizes small enough to be manageable, but still give great printed results.

The wrap up

So there you go. Not our usual top tips post, but hopefully you’ve gained a bit of an insight on the tricky dpi. And if you’re still a bit bewildered, why not get in touch so we can help you out.

Joe