I think I may have bit off more than I can chew. That being said, I am now the proud owner of a Turner Reich Convertable lens. I have read the previous thread s regarding this lens However there are still questions looming. This lens is a 12" 19.7" and 25". How do you get 12 and 19.7 to equal 25? Why do you remove the front cell? Why not the back? How do you tell how many elements each cell h as? This lens is mounted in a Betax Shutter #4 the speeds seem ok. I have not yet used the lens I will get the spare board filed out a bit in the morning. Do you think I should try to manufacture a hood that shades the shutter with no le ns on the front to reduce flare? Is there a particular sweet spot regarding ape rture? When you talk of focus shift should I look at the overall image once the lens is stopped down or just the center? I am confused about the focus shift i t just doesn't make sense. I am not sure if i am confused because of the heat or my age. not a blonde. thanks in advance for your help in sorting this out. j