I'm interested in doing more macro photography (nature macros) with my Horseman 6 x 9 camera. Because I do a lot of hiking, I don't want to get another lens sp ecially for this purpose. I have a 240 mm APO Ronar, but I won't have enough ex tension to get to 1x magnification or beyond with it. I also have a 135 mm APO Symmar, which fully extended should get me to about 1x magnificaiton. But then, thinking about it, I realized that 1x magnification on my camera will still mea n that the area photographed has to be at least 6cm x 9 cm. So I'm thinking of using a closeup filter. Has anyone used 2 element closeup filters on normal lar ge format lenses? Any ideas? How do I calculate how the different diopters wil l affect the amount of extension needed to focus closely? I thought I recalled an older thread touching on this subject, but after poking around the site for a bout 10 minutes couldn't find it. Thanks for your help.