Calling constructor from other constructor in same class

I have a class with 2 constructors:

public class Lens
{
    public Lens(string parameter1)
    {
        //blabla
    }

    public Lens(string parameter1, string parameter2)
    {
       // want to call constructor with 1 param here..
    }
}

I want to call the first constructor from the 2nd one. Is this possible in C#?