Change featured image size on single posts only

Hi there,

I was hoping you could help with changing the featured image size on specific pages?

I tried this code that I found in another form post but it changes the featured image size across the whole site (even the admin area) and I want to do it only on single posts and also event posts. So that the image isn’t cropped.

add_filter( 'post_thumbnail_size', 'ebwp_single_event_post_thumbnail_size');
function ebwp_single_event_post_thumbnail_size($size) {
    if( !is_singular('tribe_events') ) {
        return;
    }
    if( ! has_post_thumbnail() ) {
        return;
    }
    $size = 'large'; // Change to your desired image size.
    return $size;
}

Thanks :)