In Portrait of the Cardinal Infante don Fernando, the viewer is greeted by a figure dressed in rich, elaborate robes. The colors are deep and vibrant, with reds and golds dominating the palette. The background is dark, allowing the figure to stand out prominently.

The expression on the cardinal's face is serious, reflecting his high status and authority. This painting is executed in the oil on canvas medium, a common choice for portraiture in the Baroque period. The brushwork is meticulous, capturing the intricate details of the cardinal's attire and the textures of the fabrics. Light plays an important role, highlighting the face and hands while casting shadows that add depth.

The composition is balanced, with the figure centrally placed against a subdued background. Gustave Vanaise was influenced by the works of Diego Rodriguez de Silva y Velázquez, a master of portrait painting. This particular work serves as a homage to Velázquez's style, showcasing Vanaise's ability to replicate the grandeur of Baroque portraiture. An interesting fact about this painting is that it reflects the ongoing fascination with Velázquez's work, even centuries later, as artists continue to draw inspiration from his techniques and subjects.