NavigationItem button with custom image - Can't see image

I need to set a custom image on the left button for the Navigation bar.

I'm doing something like

var image = UIImage.FromFile (AppPath + "anImage.png");
NavigationItem.LeftBarButtonItem = new UIBarButtonItem (image, UIBarButtonItemStyle.Plain, null);

However I can't see the image on the button due to the tint (check image attached). I have tried setting the tint to some other color, even to Clear, but nothing seems to work.

Thoughts? Thanks, R.