Control light intensity with a UI slider

wish helps you The way to change the intensity of an AmbientLight in WPF is to change the color. If you want the light to be less intense you just set it to be a darker color (i.e. Gray instead of White or Navy instead of Blue).

I wish this help you You will have to very precisely model the nature of the dark spots for this process to work. Can you characterize whether the dark gradient is linear, exponential, power, trigonometric, or some other predictable function? Is it always exactly circular?
Having straight-line elements in the photo helps, and may provide a source of samples to calculate the nature of the dark spot from. If you treat the dark spot like a quadratic or cubic function in three dimensions (X, Y, luminance) then you can solve it based on a certain number of known points.

around this issue I don't know a plugin that implements it. But you can easily extend the lamp plugin.
You could extend the interface ILamp like

public interface ILamp
{
    ///....
    void TurnOn(float intensity);
}

public void TurnOn(float intensity)
{
    var captureDevice = AVCaptureDevice.DefaultDeviceWithMediaType(AVMediaType.Video);
    if (captureDevice == null)
    {
      Debug.WriteLine("No captureDevice - this won't work on the simulator, try a physical device");
      return;
    }

    NSError error = null;
    captureDevice.LockForConfiguration(out error);
    if (error != null)
    {
      Debug.WriteLine(error);
      captureDevice.UnlockForConfiguration();
      return;
    }
    else
    {
      if (captureDevice.TorchMode != AVCaptureTorchMode.On)
      {
        captureDevice.TorchMode = AVCaptureTorchMode.On;
        NSError err;
        captureDevice.SetTorchModeLevel(intensity, out err); // add this line
      }
      captureDevice.UnlockForConfiguration();
    }
}

public void TurnOn(float intensity)
{
    TurnOn();       
}

This might help you Here is a little sample with a table with 3 columns (id, timestamp, cnt)
then you can calculate it like this:

SELECT p.id, p.mytime, p.photons, l.photons
,TIMESTAMPDIFF(SECOND, l.mytime, p.mytime) diffsecs
,p.photons * COALESCE(TIMESTAMPDIFF(SECOND, l.mytime, p.mytime),1) as cnt
FROM photons p
LEFT JOIN photons l ON p.id -1 = l.id
ORDER BY p.id;

SELECT SUM( p.photons * COALESCE(TIMESTAMPDIFF(SECOND, l.mytime, p.mytime),1)) as cnt
FROM photons p
LEFT JOIN photons l ON p.id -1 = l.id
ORDER BY p.id;

mysql> describe photons;
+---------+------------------+------+-----+---------+----------------+
| Field   | Type             | Null | Key | Default | Extra          |
+---------+------------------+------+-----+---------+----------------+
| id      | int(11) unsigned | NO   | PRI | NULL    | auto_increment |
| mytime  | timestamp        | YES  | MUL | NULL    |                |
| photons | int(11)          | YES  |     | NULL    |                |
+---------+------------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)

mysql> select * from photons;
+----+---------------------+---------+
| id | mytime              | photons |
+----+---------------------+---------+
|  1 | 2020-02-26 12:00:00 |     100 |
|  2 | 2020-02-26 12:00:25 |      80 |
|  3 | 2020-02-26 12:01:00 |     100 |
|  4 | 2020-02-26 12:05:00 |     200 |
|  5 | 2020-02-26 12:05:03 |      22 |
+----+---------------------+---------+
5 rows in set (0.00 sec)

mysql> SELECT p.id, p.mytime, p.photons, l.photons
    -> ,TIMESTAMPDIFF(SECOND, l.mytime, p.mytime) diffsecs
    -> ,p.photons * COALESCE(TIMESTAMPDIFF(SECOND, l.mytime, p.mytime),1) as cnt
    -> FROM photons p
    -> LEFT JOIN photons l ON p.id -1 = l.id
    -> ORDER BY p.id;
+----+---------------------+---------+---------+----------+-------+
| id | mytime              | photons | photons | diffsecs | cnt   |
+----+---------------------+---------+---------+----------+-------+
|  1 | 2020-02-26 12:00:00 |     100 |    NULL |     NULL |   100 |
|  2 | 2020-02-26 12:00:25 |      80 |     100 |       25 |  2000 |
|  3 | 2020-02-26 12:01:00 |     100 |      80 |       35 |  3500 |
|  4 | 2020-02-26 12:05:00 |     200 |     100 |      240 | 48000 |
|  5 | 2020-02-26 12:05:03 |      22 |     200 |        3 |    66 |
+----+---------------------+---------+---------+----------+-------+
5 rows in set (0.00 sec)

mysql> SELECT SUM( p.photons * COALESCE(TIMESTAMPDIFF(SECOND, l.mytime, p.mytime),1)) as cnt
    -> FROM photons p
    -> LEFT JOIN photons l ON p.id -1 = l.id
    -> ORDER BY p.id;
+-------+
| cnt   |
+-------+
| 53666 |
+-------+
1 row in set (0.00 sec)

mysql>