Analog film photography and cameras

More or less for the front element, the rear element needs a c-spanner to twist the retaining ring off if I remember rightly.

The tricky part when removing the front element is replacing the focus ring/distance scale in the right place so it still focuses correctly. You more or less have to remember at what distance the focus ring is removed from the camera when you're unscrewing it, then make a note to re-attach at the same point

I think there's a youtube video somewhere that goes through it