Quote Originally Posted by Helen B

The preferable way to avoid errors caused by the possible non-neutrality of the step wedge is to have a calibrated densitometer, and to measure the step wedge in the mode that most closely resembles the way the film will be exposed (usually visual) then to measure the image of the step wedge on film in the mode that most closely resembles the way in which the paper (or next stage in the process) will be exposed.

How does that sound?


I still believe that if the step wedge has different readings in UV and Visual mode it is the UV readings that should be plugged into the WinPlotter program if that is the mode that is used to measure the densities of the second generation step wedges. And my reasoning continues to be that if you use the Visual reading densities the log density units will be of unequal length in the graphing on the x and y axis.

And there is more than the logic. When I actually tested the same film test using both values the result was exactly what I had anticipated and predicted. So there is no question but that the actual values used make a difference in plotting. Your question as to which results are right is a valid one, but I find it very compelling when a logical principle is tested and the results validate the premise.

I have posted a message about this to the btzs forum to see if Phil Davis will comment on the question. If there is a fault in my reasoning I am sure he will identify it.