CODEWITHSUNDEEP
iosobjective-cios8iphone-6avcapturedevice
Shravya Boggarapu
Shravya Boggarapu

Reputation: 592

Focus not changing even if the focuspointofinterest has changed on iPhone6 and iPhone6+ only

I am trying to change focus by changing the point of interest as mentioned.

The function always returns a YES and when I use a getter to read the new focus point of interest, it has changed but isFocusAdjusting = NO

FYI: 

 focusMode: AVCaptureFocusModeContinuousAutoFocus

 newFocusPointOfInterest: Normalized CGPoint

The focus seems to be locked at (0.5f, 0.5f) or basically AutoFocus

This code has worked on all the devices except iPhone 6 and iPhone 6+. Is there something that I'm doing wrong? Has any API call changed?

Please help

- (BOOL)changeDeviceFocusPointOfInterest:(CGPoint)newFocusPointOfInterest
                               focusMode:(AVCaptureFocusMode)focusMode
{
    NSError *error;
    BOOL ret = NO;
    
    if([device lockForConfiguration:&error] )
    {
        if ([device isFocusModeSupported:focusMode] && [device isFocusPointOfInterestSupported])
        {
            [device setFocusPointOfInterest:newFocusPointOfInterest];
            [device setFocusMode:focusMode];
            
            ret = YES;
        }
        else
        {
            NSLog(@"focus point setting not supported:{%f,%f}", newFocusPointOfInterest.x, newFocusPointOfInterest.y);
            ret = NO;
        }
        [device unlockForConfiguration];
    }
    else
    {
        NSLog(@"cant lock hardware settings for changing focus point:{%f,%f}", newFocusPointOfInterest.x, newFocusPointOfInterest.y);
        ret = NO;
    }
    return ret;
}

**EDIT : Additional observations : **

I have checked the sample apps provided by Apple AVCam and AVCamManual - Tap to focus works on AVCam but not AVCamManual same device I have tried removing code related to the manual control in the sample workspace but it hasn't yielded any results.

Upvotes: 3

Views: 1966

Answers (1)

Shravya Boggarapu
Shravya Boggarapu

Reputation: 592

This is not as much of an answer as it is a workaround.

From observation, when in AVCaptureFocusModeAutoFocus mode, the focus triggers a scan and focuses on the required point of interest and then then locks the focus (AVCaptureFocusModeLocked).

If you change mode to AVCaptureFocusModeContinuousAutoFocus, without changing the point of interest, the camera will perform a full frame focus and so the pointofinterest is rendered useless. (Determined from testing)

To imitate the continuous auto focus behaviour, I use AVCaptureDeviceSubjectAreaDidChangeNotification to monitor it manually by changing focus mode to AVCaptureFocusModeAutoFocus.

However, this is not as fast as AVCaptureFocusModeContinuousAutoFocus and I have observed a time gap of about 2-3 seconds between successive notifications.

If anyone has found a better solution, please share it here.

Note: Default camera of Apple also behaves in a similar manner. The difference lies in the fact that when the camera is moved in the default camera app of iPhone, the focus is set to AVCaptureFocusModeContinuousAutoFocus with (0.5, 0.5) as the focus point of interest.

Upvotes: 1

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