Manual focus, manual exposure and white balance, WB and AE locking

In my experience, the vast majority of time, webcams and phone cameras will get focus and exposure wrong.

I would like to be able to lock down:

• Exposure (most important; a.k.a. gain and exposure, in most webcams)
• Focus (with my experience with mobile phone camera apps, it's extremely frustrating when they keep refocusing "at the last minute" in a fraction of a second when taking the shot and they get the focus wrong, especially in low light or in front of uniform surfaces where you need to grab the focus from something peripheral to the scene. On the desktop, even the legendary Logitech C920 webcam keeps focusing in and out during use)
• White balance (somewhat less important, but still useful in many cases; lots of cameras give you an unflattering cold blue/magenta-tinted output by default, instead of neutral or warm tones)

Those things could all be set two ways:

• Touching a portion of the screen and then pressing the corresponding locking button (ex: exposure lock button), like on OpenCamera
• Using sliders and value inputs, like in CameraCtrls, particularly for desktop use, but I could also see this being useful on mobile in some situations where you want more precise control (ex: you know that your lighting's white balance temperature is exactly 5500K, or you want to set the exposure to avoid blowing out any highlights on someone's skin, etc.)