Quote Originally Posted by djkloss View Post
Thanks I made a spreadsheet to calculate reciprocity and bellows ext factor. It came out to 20 secs instead of 1. 15" bellows draw and 1 second exp. 8 1/2" lens. Sound even remotely correct?
Sounds about right, you've got nearly two stops of light loss due to bellows factor, bringing the exposure to 4 sec. then add in reciprocity. I'd say you've got all the information on the negative that you need.