Zone system and photoshop density readings

I dont have a densitometer (too expensive). I do have a 31 step wedge from which I can take readings on prints by means of a Umax 1200s flatbed scanner and the density readings provided by Photoshop. Is there a method of correlating these readings with conventional densitometric readings? I was led to consider using the computer after reading John P Schaeffer's Basic Techniques of Photography where he advocates a complicated technique for establishing densitometric values from prints using rollfilm exposed at different exposure values, a reference print and matching other prints at different exposures by means of the darkroom timer. He provides a formula for converting the variations in time to exposure values. The drawback to his systme is it requires exact eye matching of prints and use of an entire film each time. My method (if feasible) would work exactly like a densitometer reading and would require only one frame exposure through a density wedge stuck to the first frame of the film. Anybody got any ideas for translating the 255 step scale of a computer density reading into sensitometric form. Or is the computer reading too crude?

Thanks in advance

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