Hello Im really confused on the signs for f, do and di in this equation.. Please tell me if Im correct.. but here is how i presently understand if For definition sake, the 'front' of a mirror is where you would normally stand to look in a mirror, and the 'front' of a lens (like a camera) is where the objects are that you want to take a picture of. f is (+) for a converging lens/mirror, (-) for diverging. always. do is (+) when its in the 'front' di is (+) when it is a real image is this right?