Sony's Xperia Z5 family is now receiving a camera app with renovated UI, download it here

For example, you can now swipe the screen and switch between still image or video capture, which is a minor yet addition to the user experience. In addition, the various camera applications and shooting modes that are available within the app have been tweaked so as to provide an easier access. Last, but not least, Sony has improved the portrait UI, which should be beneficial to single-handed usage.
If you are impatient to get a taste of the new UI, head to the What's New app on your device and see if the updated camera app is available for you to download. In case it's not, worry not - you can sideload it and replace the one you currently use. Just click the link right below in order to get it.
Update: Additionally, if you're rocking an Xperia Z3+, you can also flash it on your handset, no root required. You can install a port of the app on any SOny Xperia Z device that has a 20.7MP camera at the back (Xperia Z1, Z1 Compact, Z2, Z3, and Z3 Compact), but you need to have a rooted handheld for the purpose. For additional info, check out this link.