This new mode allows for greater control of shutter speed and exposure.
There's a new aperture priority mode which was first featured with the third iteration of full frame Sonys (unsure whether this mode is found in earlier models). This super aperture priority mode really takes this semi-automatic mode to the next level. It's also a must if you shoot street photography. Here's a quick set-up guide.
3 Step Set Up
1. Set the control dial on top to A for aperture priority.
2.. Go to tab 1 in menu, page 9/14. - Change ISO to ISO AUTO - Change ISO AUTO Min. SS to desired minimum shutter speed. For example, 1/500.
3. Change your aperture to desired setting. For example, F1.8.
What this mode does is assigns a minimum shutter speed based on what aperture you dial-in. So if you used the above settings, your shutter speed would remain at a constant 1/500 of a second, allowing you to freeze most action while maintaining a wide aperture value of f1.8.
So what happens when the light (or lack thereof) starts to affect the exposure to the point where your dialed-in settings won't produce an acceptably exposed image? The Sony A7iii would first increase or decrease your ISO settings to compensate. If your ISO is forced to go beyond the minimum or maximum values of what you've already set up (or Sony's default), then the shutter speed will either be decreased or increased to compensate for exposure. If your shooting environment becomes darker, for example, then the shutter speed might be bumped down to 1/250 or slower to compensate for low light. Or conversely, may be raised up to 1/1000 or higher if over-exposure would result otherwise.
Things to keep in mind
* Be sure that ISO AUTO is always selected. I use mainly manual and aperture priority, so I'm constantly switching between the two. Naturally, the ISO is going to be an important thing to keep in mind or it would render aperture priority useless.
* If your ISO or shutter speed values become impossible to work with in changing conditions, or you find yourself constantly having to adjust your aperture priority, it may be time to switch to manual mode to get the correct results.
Customizing your Fn menu for quick access (great for street photography)
If you're going to be using aperture priority frequently, then it's best to program your ISO AUTO Mins. SS mode into your function menu (Fn) on the back of your Sony A7iii. This will allow for quick access when switching between aperture priority and other modes. The picture below shows what it looks like in my menu. Keep in mind that I've got other customized features already added, so your Fn options will likely look different.
How to customize your Fn menu