Stepwedges for Dichroic VC calibration

Hi all
I'm close to have finished the shed in which Im about to install a darkroom and Im planing the next moves (Building tables for enlarges, countes and storage etc). I figured I will Calibrate my two enlarger with dichroic heads (Omega D3 and Durst AC707) as in "Way Beyond Monochrome". So Im in need of some stepwedges, right? Stouffer has some: T3110; TP12-31 and TP4X5-31. Question is which to get and do I need 31 steps or will 21 do?
Best regards

Soren

31 spteps have more info and accuracy but they take longer to evaluate the data. 21 steps are enough, but you might want to use the step wedges for other tests and then 31 steps might be needed. So, I recommend a 31-step test tablet in the size of your negative. To save shipping costs, and you need one anyway some day. Also get a 31-step version in 4x5 for contact printing. Don't get the calibrated version of any step tablet. They are terribly expensive and all they offer is a list of accurately measured densities. You don't need that. get all test tablets as non-calibrated.

Hope this helps.

Hi Ralph
Thank you for the very precise answer. re 31 vs 21 steps, I think I read something somewhere about 21 steps being equal to half stops and 31 to 1/3 stops, commends on that?
Best regards

Soeren said:

I think I read something somewhere about 21 steps being equal to half stops and 31 to 1/3 stops, commends on that?

Click to expand...

That's correct for the Stouffer wedges, yes. We use the 21 step one for Analyser / ZoneMaster calibration. Each step is half a stop and corresponds to 15 ISO(R) contrast units.

One advantage of 1/3 stop steps is that corresponds to the steps in standard ISO film speeds, right? I don't actually see how that would matter, especially for calibrating paper processing.