Does anyone know how to do it?
I would like to implement Facebook or Disqus comments.
I am using the gallery with the shutter effect.
Thanks for your help!
Would Jetpack's new Carousel module work for you? It works with the native WordPress galleries, and IMO, may be a better fit for you as it allows comments on images in a gallery.
Check out the demo of Jetpack Carousel here.
NextGen supports templates so you could create your own template and include the comments system that way.
You can read up on templates for NextGen here: http://www.nextgen-gallery.com/templates/
In short you copy the template files from the plugin into your themes folder and then modify as required, such as including comments. Then in your shortcode you reference which template to use.