Do I need full 300dpi resolution photos for designing a poster?
I'm working on a poster for a local event. It has a photograph in the background. The poster itself is designed to be 11x17, which at 300dpi is about 3300x5100.
Now the photo in the background does not have to be completely crisp, since it is behind the text and can be a little blurry.
I'm just looking at istockphoto and wondering what size image to buy. I don't think I need the full size, but I have no idea which I can get away with.
If you'll be going to a digital print shop to make the posters (which would be usual for a small run for a local event), you'll be fine at 150 ppi, and for a background image you probably wouldn't be in trouble at 100 ppi, particularly since it likely won't contain a lot of high-frequency detail that would conflict with your text.
An 11x17 poster is mostly going to be viewed from a lot more than 10 inches away, so that also reduces the resolution requirement.