Still life photography is another genre with a large gray area between fine art and documentary photography. The difference is, again, the purpose of the photo and the importance of the subject. Are you taking the still life picture because the subject is special, and you want to show it to others? Or are you experimenting with an idea or technique to create art?
For instance, you can find countless images of food on Instagram, but the majority are spontaneous and documentary in style. They show a special location, dish, or moment in time the photographer wanted to capture and share.
By contrast, in fine art food photography, the photographer’s imagination is clearly evident in the picture. It’s not a memory; it’s something the photographer thought about and then executed artfully.