: How much can I scale a photo before the quality will degrade I'm thinking of purchasing a photo on iStock to make a poster size print. I'm pretty familiar with resolution and how it works,

@Moriarity648

The image size (5474 x 3649) you have is good enough to print at any size you want - even billboard size - you don't need to do anything to it. It doesn't need to be rescaled or resampled. In fact I strongly advise against doing that or you will degrade the image quality.

The reason this works is because of the viewing distance. A large format print or even a billboard is designed to be viewed from a distance.

You can think of it like a huge TV screen - close up you can see the dots/pixels that make up the display screen, but from normal viewing distances, from a position where you can see the entire screen comfortably, the dots/pixels are not visible.

Large format prints are generally printed at somewhere between 72 to 150dpi. 300dpi is for prints you are going to view close up - such as A4 size, or in a publication. If you print your image at 30" high, you'll be printing it at around 182 dpi - this is absolutely fine for an image such as the one you describe.

For this same reason, huge billboards are often printed at even lower resolution, like 20dpi or less. These are designed to be viewed from a passing car, or from across the street.

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