Lightbox is basically what you see from some websites like Flickr or Primfeed.

The script links for this type of feature is -

It also allows the user to stay on the product page without opening a new tab. That is unless someone wants to open an image on another tab for their own reasons.

With this the background is darkened to allow people to view the product image better. It is also usually paired with a zoom in feature as well. Which zooming-in probably would be best to add with the lightbox seeing as how when using a mobile device the responsive design allows you to zoom in to get better details of the product your buying, where you "normally" can't do this on a desktop. That is unless you have a touch screen monitor or you setup some accessibility settings to zoom in through one of your programmable mouse buttons and scroll wheel.

With that said, this at least gives desktop users an on par or better product image view as mobile devices. Plus on desktop I've tested some product images on another tab where the surrounding background is black so as to make the product image more eye popping to view and it works quite well but it would be easier to see this through Lightbox use instead for most users.