We recently deployed krpano HTML5 on a 65" UHD touch tabletop surface. We found that when people zoomed all the way in to an image until they reached the maximum zoom level, but kept spreading their hands/fingers beyond that, the image would stop zooming as it should. However when their hands/fingers were drawn closer together to zoom out, nothing would happen right away, until they'd brought them close enough together to reach the previous zoom-out extent.
A nicer behavior would be that when fingers/hands are brought closer together, zoom out should always begin, even if the previous gesture took the image beyond the zoom in limit.