DPlot

With a little effort, yes. If I understand the data in your link correctly, here's a plot of it:

That's just the ticket, David, many thanks. I was having some trouble getting data into DPLot (likely not helped by running it on a Mac under Virtual PC). I installed the trial version today on my XP ...

DPlot looks like it *could* be just what I need, but I'm not sure of what a 3D surface plot would look like, generated from fairly sparse data. - Is there a way to have it do something like a b-spline fit in 3D to scattered data points?

The data is from a lens-testing program, it consists of 17 ...