> almost like some imaginary need for a specific shutter button to press to take a photo on a phone (just touch the screen!).

I've always wanted a shutter button on my phone, because of what it would imply: the ability to take a picture instantaneously, as the first action that wakes the phone from sleep. I often miss shots because of the six seconds required to get from my phone being in my pocket to having the Camera app open.

Got an iPhone?

1. Pull out phone. 2. Press power button. 3. Swipe the time left (don't unlock) 4. Press volume down button to take photo.

Two seconds tops from photo op to photo!

Note: You don't have to swipe the time, you just want to avoid swiping a reminder and the time is an easy and guaranteed-to-work target.

You're missing the point. All phones have a camera shortcut.

OP's point is you shouldn't even have to have an additional step, however short it is.

Imagine though the millions of photos a phone would shoot in a pocket.

My xperia has a dedicated camera button.

Certainly a better way, but my gripe above is not just with volume buttons but with other things such as EQ, panning, time delays and a million other things that audio software can control.

I am guessing that screen UX designers wrestle with the same constraints that physical audio hardware manufacturers to - that of space restriction, and cramming as much as they can into a given space.

Hence I guess why things like recording consoles have a slider for the critical volume adjustments, but rotating knobs for other things like panning, EQ etc. above that.

Volume is one thing I don't mind seeing as a vertical slider, but then would panning be a horizontal slider? I actually prefer a round knob for that because the knob position is a better resemblance of the 360deg sensory perception around my head when setting the stereo space.

Albeit a true 2D control surface works much better. (A control rectangle which is a cross product of two sliders.) Pan cannot give you 2D positioning, even when combined with loudness or approximation thereof.

To be honest, I prefer the physical shutter button over tapping my screen on my phone when taking pictures.

Especially since screen tapping could be registering a "refocus to this point" action. Also since camera phones have no viewfinder, I use the screen to compose my shot. So to avoid obscuring what I am going to take a picture of, I keep my hand clear of the screen most of the time. That makes the act of triggering the shutter a more visible and deliberate act than just pushing a button that my finger is already touching. These probably don't matter to most people but are fairly frustrating to me. (the fact that I almost always shoot landscape, not portrait, may be the cause of the discomfort for me, since it changes my hold on my phone to something more like the hold on a camera.)

With most sensors having a 4:3 aspect ratio and smartphone displays having a 16:9 (or wider) AR, there is no need to block the image being composed with any fingers. The blank areas are filled with all relevant controls and a virtual shutter release button.

I don't believe the parent meant a physical shutter button, but a specific area on screen designated as the shutter button instead of the much easier, "anywhere".

Well, having "anywhere" be the shutter button means tap to focus won't work.

Use the volume down button on an iPhone.

In landscape orientation, stock Android "helpfully" keeps the shutter button on the right side of the screen at all times even if you rotate it. Because left-handed people never take photos. -_-

On many (most?) phones, the volume buttons act as a physical shutter button. I don't recall the last phone I saw which doesn't have this feature. iPhone, various android phones...

Or a UI control mimicking an old-style rotary dial in a phone app. (Although to be fair, the rotary dial in old phones was terrible UX brought about by a purely technical design decision - on the other hand a physical volume dial in a real amplifier is a pretty intuitive control.)

what's the second dimension on rotation? you can completely describe it using the angle.

Sliders take up more space for the same "travel" though.