I think it a 2 f/stop increase, which is a 4x increase in exposure. Sherman Bloom shermanbloom@xxxxxxx http://www.phototov.com On Feb 28, 2011, at 6:49 PM, Jim Brick wrote: This has been answered, but as a memory jogger... it is a 2X extender, so the exposure increase needed is, likewise, 2X. Jim Brick Sunnyvale, CA http://www.photomojo.org/vip.swf On Feb 24, 2011, at 10:15 PM, James wrote: > how many stops do I adjust for