How to obtain detailed zoom specs for iPhone camera(-s)? [closed] - ios

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I'm making a zoom control for my app, and I'd like to make it advanced, like in default camera app from Apple: sample
I did some research, and still have some questions about it.
Is it possible to get focal length value programmaticaly? There are labels like 13mm, 26mm for different back cameras in the default app, but there is no such property on AVCaptureDevice. (It is probably needed to determine zoom values, see the next question)
How can we determine zoom values to display in UI? The thing is that AVCaptureDevice's minZoomFactor always starts from 1x, but in the camera app we can see that on devices with ultrawide camera the scale starts at 0.5x, so there should be some way to map this values onto each other. As I understand, Apple considers "usual" back camera as default (that is, 1x), and all other values are relative to it: 13mm is 0.5 * 26mm, so the first value on iphone 13 pro zoom control will be 0.5x, the second value is the "default" and is 1x (26mm), and telephoto camera is 77mm, so the third value is 3x (26mm * 3 = 78mm ~= 77mm). Please clarify how it is actually calculated and correct me if my assumption is wrong.
What is the correct way to get max zoom value? If I try AVCaptureDevice.DiscoverySession(deviceTypes: [.builtInTripleCamera], mediaType: .video, position: .back).devices.first!.maxAvailableVideoZoomFactor, it says 123.75 (iphone 13 pro), but in the default camera app max zoom value is 15x. Why is it exactly 15x and where does it come from? (My assumption is that max digital zoom for all iPhones equals to 5x, so on 13 Pro telephoto camera zooms 3x as "usual" camera, thus we get 3x * 5x = 15x max zoom)
Is there any universal way to get "the best" (i.e with all features) camera? For example, now I can specify [.builtInTripleCamera, .builtInDualWideCamera, .builtInDualCamera, .builtInWideAngleCamera] for discovery session and pick the first item in devices array, but if Apple will release, lets say, some ".builtInQuadrupleCamera" in a couple of years, this code will have to be modified, because it won't include it automatically.
To sum up (TL;DR version):
As I suppose, final code should look something like this:
let deviceTypes: [AVCaptureDevice.DeviceType]
if #available(iOS 13, *) {
deviceTypes = [.builtInTripleCamera, .builtInDualWideCamera, .builtInDualCamera, .builtInWideAngleCamera]
} else {
deviceTypes = [.builtInDualCamera, .builtInWideAngleCamera]
}
let session: AVCaptureDevice.DiscoverySession(
deviceTypes: deviceTypes,
mediaType: .video,
position: .back
)
if let device = session.devices.first {
device.getUIZoomValues()
}
extension AVCaptureDevice {
func getUIZoomValues() -> [Float] {
// Hardcode. Seems like all iPhones limit digital zoom to 5x
let maxDigitalZoom: Float = 5
// fallback for old iOS versions
guard #available(iOS 13, *) else { return [1, maxDigitalZoom] }
let uiZoomValues: [Float]
let factors = virtualDeviceSwitchOverVideoZoomFactors
switch deviceType {
case .builtInTripleCamera, .builtInDualWideCamera:
// ultrawide camera is available - starting zoom from 0.5x
let firstZoom: Float = 1.0 / factors.first!.floatValue
uiZoomValues = [firstZoom] + factors.map { $0.floatValue * firstZoom } + [firstZoom * factors.last!.floatValue * maxDigitalZoom]
case .builtInDualCamera:
// no ultrawide. Starting from 1x
uiZoomValues = [1.0] + factors.map { $0.floatValue } + [factors.last!.floatValue * maxDigitalZoom]
case .builtInWideAngleCamera:
// just a single "usual" camera.
uiZoomValues = [1, maxDigitalZoom]
default:
fatalError("this should not happen on a real device")
}
return uiZoomValues
}
}
2 main concerns about this code:
1 - We have to hardcode maxDigitalZoom. Is there any way to get it programmaticaly? Apple states 5x in iPhone specs, and there is AVCaptureDevice.maxAvailableVideoZoomFactor, but those values are different (for example, iPhone 13 pro has 15x in specs vs 123.75x in maxAvailableVideoZoomFactor).
2 - Case builtInDualCamera (iPhone XS Max, for example). All the code above relies on virtualDeviceSwitchOverVideoZoomFactors var, which is available only from iOS 13, but builtInDualCamera is available from iOS 10.2, so what will happen if user has XS Max? Will it work on iOS >= 13 but break on earlier versions? Or it will not work at all?

Answer 1

Questions in order:
I think not
Works for me:
Created dictionary var zoomFactors: [String: CGFloat] = ["1": 1]
Than manage AVCaptureDevice?
I think u can play with getApproximation() to achieve the goal
No
Code Questions:
No. but i think one of the easiest method it's to play with getApproximation() idea
I believe it will be crash