plane track and scaling problems help please!!

Hello im having trouble with scaling issue for some reason. im trying to have the full picture frame covered by the head in the third picture i uploaded. however when i connect it to the plane track node it scales it down and leaves the white around it I dont understand but when i directly plug the image node directly to the viewer node i get the proper scale im looking for like the 2nd image can anyone help please this is frustrating i googled and watch video tutorial which all works fine also the image of the head i want to use is png so how do i scale it to the right size? hopefully that makes sense