1枚のバインダーに収まるくらい makes little sense to me in this context, either. バインダー in Japanese normally refers to that ring binder used to bundle loose leaves. However, loose leaf binders are normally counted using 冊, not 枚. In addition, a binder can contain hundreds of pictures, but you need something that is small in this context:
I could watch everything in one view enough to be contained in ～.
(一望 = to have one view that contains everything in the scene. It usually means "panoramic/wide view", but in this context it's about "compact/at-a-glance view" like this.)
Assuming this バインダー is not a loose leaf binder.... so what is the thing 1) that can be called or mistaken as バインダー, 2) that is inherently small, and 3) that may be counted with 枚?
- Maybe the author meant "clipboard"? Looks like バインダー is a rare synonym for this (I didn't know this, but see this article).
- Maybe the author meant ファインダー "(camera) viewfinder"?