Change image size in Shortcode

I have used this shortcode on my homepage of a website.

<?php echo do_shortcode( ‘[projects limit=”12″ columns=”3″ orderby=”date” order=”desc” exclude_categories=””]’ ); ?>

Currently the images are being pulled through at 1500px width and 2000px height, is there any way i can change these numbers so they are pulling through smaller to improve site performance