I am using WP Show Posts Pro to show a gallery of images in 3 columns. The images are displaying correctly with the ‘srcset’ attribute so the browser can download the most appropriately sized version of the image. However, the ‘sizes’ attribute is showing the WordPress default setting. E.g.
sizes="(max-width: 1200px) 100vw, 1200px"
This means the browser is downloading a version of the image suitable for the full-width of the viewport (100vw), even though it only requires an image to be a third of this (33vw).
How can I change this attribute for my WP Show Posts images?