PT Serif Caption
Google Fonts · Alexandra Korolkova · 2010

The caption-specific cut of PT Serif, optically adjusted to maintain crispness and legibility when used at small sizes.
About
PT Serif Caption addresses the optical challenges that arise when a text serif is scaled down to caption sizes, adjusting spacing and weight to preserve distinction between letterforms. Available only in Regular weight, it is best suited to supporting roles such as image captions, footnotes, and sidebars within PT Serif–led layouts. Its Cyrillic support keeps it consistent with the broader PT family's multilingual scope.
Classification
PT Serif Caption is an optical size variant of PT Serif, adjusted with lighter overall colour and more open spacing to remain legible at small display sizes. It is a single-weight solution aimed at captions and supplementary text.