When should a Computed field be used in Sitecore?

A Computed field in Sitecore is used specifically to derive a value based on existing data in other fields, which is particularly useful for scenarios where you want to generate or calculate values dynamically. This means that when data is indexed for search or other operations, the computed field can take the values from other fields, perform calculations or transformations, and store the resulting value in the index.

Choosing this option aligns perfectly with situations where you want to generate a value that is not explicitly stored in the content item but is instead a runtime calculation based on user input or other fields. This functionality allows for greater flexibility and ensures that the indexed data is always relevant and accurate, reflecting the latest changes in the source fields.

Other options provide contexts that do not align with the purpose of a Computed field. For instance, storing images, displaying data without modification, or managing large datasets do not involve the calculation of values but rather the direct handling or retrieval of existing data. Thus, these scenarios do not benefit from the properties of a Computed field in the same way as the correct answer does.