I have purchased used F80 macro lens for my 645. There is a ring on the front of the lens with two click stops and there is a red and green scale on the focus ring. I suspect these two are related. Ive checked focus while changing the front ring position and cannot see any difference. What is the purpose of the front adjustment and how is it used? Thanks
The spacer is about 44mm of extension, so it is specifically matched to the 80mm macro lens. That said, if you don't need specific magnification ratios, you could use any combination of extension tubes to get closer focusing. It might be convenient to have the spacer to easily determine bellows factor with the focusing scales on the barrel of the lens.