Print your photos as posters

Get the most from your photos’ pixels to get optimal giant printouts

- Keith Martin

Okay, you’ve taken your personal ‘shot of the year’, a photo so stunningly great you want to blow it up to a giant size and put it on your biggest wall. The trouble is, even a 12MP shot from an iPhone 7 can barely reach 40cm across without starting to look soft, and shots from the iPhone 6 and earlier models only just scrape past 30cm wide. So how did Apple create those bigger-than-duvet-sized ‘real iPhone shots’ for its billboard adverts? The answer is actually simple: interpolation. The images have been processed for large-format printing by dramatically boosting the number of pixels and applying careful sharpening.

Repeat after me: it’s not cheating, it’s optimising. Photographers and designers tweak and tune images for different kinds of output all the time. It’ll help to know a bit about image resolution and to get hold of software to do the optimisation. First, though, make sure your photo really is technically as well as creatively good. If it’s a bit fuzzy, if the focus is off, or there’s camera shake, that’s going to be magnified along with the scene itself. The old programmer’s phrase “garbage in, garbage out” is worth remembering; start with the best originals you have.

Pixel perfection

The secret to image resolution is actually very simple. Never forget this fact: a digital photo is just a grid of pixels, like a sheet of graph paper with extremely fine squares. If you simply stretch that grid to fill a larger space you make the squares bigger. Take this enlargement too far and that grid becomes noticeable; the image looks pixellated and we call it low resolution. Scale the same image grid down to a smaller print size so we can’t see the pixels and we call it high resolution. It all depends on how large we want to use the image.