A very useful tool

In Ralph Lambrecht's excellent book, "Way Beyond Monochrome", a process is described for systematically testing a film type and developer combination, to work out your personal exposure index (EI) and development times for N-2 through N+2 development, using an Excel spreadsheet he'd created to analyse the data. There used to be a web site that held various resources to accompany the book. Among these were a PDF copy of the film testing chapter, and a copy of Lambrecht's spreadsheet.

That web site is no more, but I downloaded those two files in 2013, and have kept them available here since. Here are my unchanged copies of the PDF of the chapter and the spreadsheet.

Fixing a bug in the spreadsheet

There is a minor bug in the spreadsheet:

On the "Input Data" sheet, you can (optionally) change the "Relative Dmin/Dmax" values in cells K49 and L49. If you do, you won't get the expected effect. This is because the difference between these two values (the wanted range) should be used in a few places, but isn't; instead, the constant 1.2 is.

On the five "Curve" pages, there are formulas in cells K49 and L49 to calculate the "N" offset, and they are, respectively,

=(2.1-(1.2/K48))/0.3

and

=(2.1-(1.2/L48))/0.3

Those "1.2" constants shouldn't be constant; they should be the calculated difference between the absolute Dmax and Dmin in K44 and K43, so the formulas should be changed to

=(2.1-(($K44-$K43)/K48))/0.3

and

=(2.1-(($K44-$K43)/L48))/0.3

On the "Summary" page, the constant 1.2 is again used in cells P33 through P37. Here, the range end points aren't readily available on the page, so fetch them from the "Input Data" page by replacing "1.2" with

($'Input Data'.$L$49-$'Input Data'.$K$49)

For example, cell P33 should become

=(2.1-(($'Input Data'.$L$49-$'Input Data'.$K$49)/P13))/0.3

and copying it to P34 through P37 will adjust that reference to P13 correctly for each copy.

Here's a copy of the spreadsheet with the above changes in place. It has, in other words, been modified by me, in a way I believe to be correct. I may have made mistakes. If so, blame me, not Ralph!