How do you tell the difference between naturalistic and impressionist artwork?

Realism was an attempt to portray the lives of ordinary people and their environments. Romantic and Renaissance painters had tended to focus on idealised subjects and situations. Realists painted people as they were, at work or at play. They aimed to observe and then capture faithfully the scene they were painting, rather than adding a layer of interpretation. The movement was partly a response to the social change brought about by the Industrial Revolution.

The naturalists aimed to paint natural life as accurately as possible. Like the realists, they aim to show reality rather than interpretation. Naturalist paintings are very detailed, as details increased the accuracy of the painting. Naturalists were heavily influenced by Darwinian ideas about the strength of nature, and the lack of ability of humans to combat the forces of nature. Like realism, naturalism was partly a reaction to the Industrial Revolution and their Darwinian attitudes reflected this, according to Michael Arnold Art. They rejected contemporary ideas that technology could overcome nature.

Hope it helped! :)

All of the above have been used in film noir.