* The subject: Some subjects are better suited to landscape or square formats. For example, a portrait including a wider view of the subject's environment might benefit from a landscape format.
* The story you want to tell: The format can influence the narrative of the portrait. Portrait formats emphasize height and verticality, focusing attention on the subject's face and upper body. Landscape formats can include more of the surroundings and create a sense of place.
* The environment: The surroundings of the subject can greatly impact the choice. A beautiful landscape or architectural backdrop might be better showcased in a landscape format.
* Compositional elements: How you arrange the elements in the frame, such as leading lines, negative space, and symmetry, can work differently in each format.
* Intended use: How the portrait will be used (e.g., print, social media, website) can influence the best format. Social media platforms often favor square or portrait formats for mobile viewing.
* Artistic vision: Ultimately, the choice is up to the photographer and their artistic vision.
In summary: While portrait format is often a good starting point for portraits, don't be afraid to experiment with other formats to see what works best for your specific subject, environment, and artistic goals.