Cargo Features

Nom-Exif has no features set by default.

[dependencies]
nom-exif = { version = "1.2.0", features = ["json_dump"] }
json_dump = serde

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

serde json_dump?