The preferred resolution is 350ppi. However, since photo sizes will not be finalized until print time there is no way to say exactly how big your image will need to be. To get an idea of how big your image can be used consider the following it will be used at:
- 2-page spread: 17" wide x 350ppi = 5950px wide
- Full-page: 8.625" wide x 350ppi = 3018px wide
- Maximum height: 11.125 x 350ppi = 3893px wide
- Smaller sizes: Most images used will be smaller than the above measurements. For example an image used at 2.5" wide would only need to be 875px in width.
Your image will only be considered for placement where it's resolution is high enough to produce a good quality product. Resizing your image to a higher resolution in an image editor will result in a fuzzy images and will not be accepted.