How can you zoom on image assets in the cloud asset viewer?

I've been using the web interface for viewing image assets. I am typically working with very "tall" images, which are comps of full-length webpages. Because they are so tall, they are often zoomed out quite far. If I click on the "full screen" expand icon, it doesn't really do anything of value - it still shows me the entire tall image. Is there any way, within the web interface, to zoom in on a particular section of a high-resolution image (specifically PNGs of JPEGs)? If I use the browser's native zoom function, it actually makes the images smaller.