Hi Bill,
Thanks very much for the response. Sorry if I am coming across a tad vague - this is a new area to me and I still have much to learn here. :) That is something of an understatement...
I suppose I am trying to characterise the whole process - paper, negative and ink via the linearisation of the curve. All the processes I have read about talk about printing a step wedge to the transparency film, establishing the baseline exposure to produce dMax on a given paper and then printing/developing the step wedge onto the chose paper (silver, pt/pd etc..). They all then explain how to scan this developed step wedge and before taking any measurements defining the white point as wedge step 1 and black point as wedge step 21 (in order to effectively measure the differences between analogue vs digital wedges this step seems absolutely vital). It is this scanning part that I would like to try and figure out an alternative.
I would like to be able to read the values of the each step as L* (via the lab colour space) and utilise these readings to plot the correction/linearisation curve for the given paper, ink, transparency combination. What I keep getting confused about is how do I handle the black & white points. If I read the wedge black point with a spectrophotometer I will probably get a reading of say L*=5 and a white point of L*=96 (for example). In the digital domain, the first step would be to fine these values as L*=0 and L*=100 respectively. The question hinges on how do I go about normalising the curve with this taken into account?
One thing I have thought "may" work would be to plot the curve using the L* reading taken with the spectrophotometer (0%, 5%, 10%, 20%, 30% - 95%, 100% etc...) including the black & white points of L*=5 and L*=96 (respectively). This would produce a low contrast curve with no dMax or dMin being achieved. Once this is done using the levels tool I could then define the black and white points as L*=0 and L*=100...? Would this work in anyones opinion? The problem here is every print will require the low contrast curve to be applied, then corrected with the levels tool for dMax and dMin to be achieved.
I hope this makes sense... :) My head hurts, the more I read on this the more confused I seem to become. I hope I have explained better and that it does not come across like the ramblings of lunatic :)
Much appreciated,
Karl