Will uploading a NextGEN gallery with high res images slow down my WP site?

Hi guys,

I am working on a project for a Photographer who wants the ability to upload high resolution images into a client gallery for purchasing high res. downloads etc. I am using NextGEN gallery for this purpose.

This might be a silly question, but will uploading all these high res images to a NextGEN gallery slow my wordpress website down? Or does the gallery automatically resizing the images for the gallery display get around this problem?