Not to be confused with file size (which is related to the resolution of the photo), the scope of a photo is the amount of visual information side to side and top to bottom.
Traditionally, when photographers shot a portrait for use on the web, they cropped it relatively close to the subject, omitting the “unnecessary” background (and sometimes foreground) above, below and to the sides. The resulting image is said to have “narrow scope.” (Also called a close-up.) A narrow-scope photo might be cropped out of a larger scene, or the photographer might have “tightly framed” the original shot, effectively cropping on the fly.
More recently, however, faster download speeds and better file compression have allowed us to use larger photos on the web. While we could make the narrow-scope photo bigger on the page, it can be more impactful to include more of the “unnecessary background”—more of the scope—and overlap design elements such as text or other visuals. This photo is said to have “wider scope.” (Also sometimes called a long shot.)
In fact, starting with a high-resolution photo with lots of scope allows web designers the flexibility of placing the subject to the right or to the left—to allow for overlapping elements—and even to allow for more of the original scope to show through during parallax scrolling, a slider effect or a static background.
A narrow-scope photo can always be cropped from a high-resolution, wide-scope original, but never the reverse. Wide shots offer more options. That’s why photographers shooting for the web today often include more in the scope of their photos by “shooting wide.”