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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, but before forking out the money and ending up with a print that might not be how I want, I just want to see how much I can scale the image, which is now 5474 x 3649 px (18.25 x 12.16 in.) @ 300 dpi, before the quality shifts. I'd like to keep it as sharp as possible, but I did want to have either the height or width at least 30in. If I try to do that with this particular image will it noticeably ruin/distort the quality?