Quote Originally Posted by bmac
The wood back / spring locks / padding on the wood (I used automotive headliner) all work together to create a presure that will make the neg to paper sharp (sharp enough for my bad eyes at least. Glass and gravity don't even compare.
Brian, your comment about glass and gravity as opposed to spring tension is accurate in my experience. The same principle applies to spring tension as compared to the pressure exerted in a vacuum frame when one works with larger negatives and paper. Prior to buying a vacuum frame, I encountered not one person that told me that spring back frames equalled vacuum frames when one moved into ULF negatives. Had I found someone that shared a contrary experience with me then I would not have spent the money on the pump and frame. My experience with the vacuum frame has supported and reinforced what I was told.

As I have related earlier I do use a 8X10 spring back frame when I do a limited number of prints of that size.