Re: gum "curves"
I agree with this. There is absolutely nothing unpredictable about curves. If you have done your testing, and have control of your process, you will get consistent results. Data in, data out. If you can not repeat results you don't really control the process, and you will get surprises, curve or no curve.
One thing I have noticed is that some people expect PDN, and other curve producing systems, to provide a magic carpet ride. They won't. Before investing in any methodology for making curves I would recommend the purchase of a Stouffer step tablet, then print and test your process until you can repeat results. If you can not repeat results no curve is going to help.
Just the other day I pointed out that there's a serious flaw going on in your argument here. When used correctly, PDN (and curves in general) eliminate any and all guesswork. Anyone who tells you that their PDN curves are unpredictable (no matter what the process) is not using the system correctly. I can tell you from my own experience (as well as others, I'm sure) that making curves for gum has been extremely reliable, and has never been unpredictable. Camden Hardy camden[at]hardyphotography[dot]net http://www.hardyphotography.net