Le Sidanier began his artistic journey at a young age, studying at the École des Beaux-Arts in Paris. He was initially influenced by the Impressionist movement but later developed his own unique style, characterized by a delicate and poetic approach to light and color. His works often featured muted tones and soft brushstrokes, creating a dreamlike and ethereal atmosphere.

One of Le Sidanier's most renowned paintings is "The Pink Cloud," painted in 1907. This masterpiece showcases his ability to capture the fleeting moments of nature and the play of light. The painting depicts a solitary figure standing on a bridge, gazing at a pink cloud floating in the sky. The scene exudes a sense of tranquility and contemplation, inviting the viewer to immerse themselves in the peaceful ambiance.

Le Sidanier was also known for his interior scenes, particularly his depictions of dimly lit rooms and quiet corners. His painting "The Lamp" is a prime example of his mastery in capturing the interplay of light and shadow within an intimate space. The solitary figure sitting by the lamp creates a sense of solitude and introspection, inviting the viewer to reflect on their own thoughts and emotions.

Throughout his career, Le Sidanier's works were exhibited in prestigious galleries and salons, including the Salon des Indépendants and the Salon d'Automne. He gained recognition for his unique artistic vision and his ability to evoke a sense of tranquility and introspection through his paintings.

Le Sidanier's art was deeply influenced by his love for nature and his fascination with capturing the essence of solitude. He often sought inspiration from the landscapes of Brittany, Normandy, and the French countryside, where he would spend long periods of time immersing himself in the peaceful surroundings. His paintings reflect his deep connection with nature and his desire to convey its beauty and tranquility to the viewer.