Exposure factors for Mamiya Universal extension tubes

[borrel]

Has anyone come across a simple calculator or formula for figuring out the exposure compensation factor necessary when using extension tubes on a Mamiya Universal or Super 23? Robb Smith's Mamiya book (p. 235) gives a factor of +6 when using all 5 rings with the 100mm 3.5. Is the light reduction linear or exponential and how do I go about figuring the values for other combinations of rings?

- Børre Ludvigsen <b at hiof dot no>

 

[oftheherd]

Try Butkus.org. If you go to http://www.butkus.org/chinon/mamiya/mamiya_universal_black/mamiya_universal_black.htm you can find a complete manual. The second section on his Universal site has charts and may give you what you are looking for.