Sony didn't try too hard to make its top megazoom for 2013 much better than the one from 2012. Basically, it bumped the resolution up from 18 to 20 megapixels and popped on a new zoom lens: 50x f2.8-6.3 24-1200mm.
The HX300 has a control ring around the lens barrel that can be used for zoom or to manually focus. Speaking of focus, Sony promises faster autofocus speeds and improved optical image stabilization.
Also, Sony improved its Superior Auto mode on these cameras for better results when shooting moving subjects. Superior Auto combines Sony's regular Intelligent Auto with its multishot modes. Because of how the multishot processing works by layering multiple shots, using it with moving subjects doesn't work well. Sony's added motion detection to the mode, so that if the subject does move, it won't use the multishot processing.
In order to put its 25-500mm lens in body this small, Sony took a 1/2.3-inch 21.1-megapixel Exmor R sensor and only used 18.2 megapixels of it, basically making an already small sensor even smaller. Sony also stripped out the GPS receiver found in its predecessor -- the HX30V -- but kept the Wi-Fi that can be used for transferring photos to a smartphone, tablet, or PC, or for using your device as a wireless remote screen and controller for the camera.
As of its announcement, the TX30 at 0.6 inch thick is the world's thinnest waterproof camera, because nothing is more important for a rugged camera than being really thin. Underneath its slide-down lens cover is a 5x f3.5-4.8 26-130mm lens with LEDs on each side of it for macro shooting.