Search engines will typically look for some textual signals that indicate the subject of page content, such as H1s, titles, alt text, transcriptions, etc. Pages with relatively little content run the risk of being classed as doorway pages by search engines.
The bottom line is that thin content should be avoided, as search engines want to populate their index with high-quality results which, in most cases, means providing in-depth and valuable content that users will find useful.