Hello,

It shows featured images.

The first featured image is the preview AND is inclded in the gallery

To make the preview thumbnail and display full image in the gallery is custom work.

thanks

Hi there you need to modify the implementation of /sections/portfolio_section_slide.php or /sections/portfolio_section_overlay.php depending on the hover effect.

Replace

$full_image = wp_get_attachment_image_src(get_post_thumbnail_id($post->ID), 'full');

with

$full_image = wp_get_attachment_image_src(get_post_thumbnail_id($post->ID));

or whichever size you prefer.

https://codex.wordpress.org/Function_Reference/wp_get_attachment_image_src

thanks