Hi Neil,
Yes, that would explain it as Pro-PiezoDN-PtPd-PrintOut.quad is not actually a digital negative curve. It is a starting curve designed to be “too much” nearly everywhere so that the linearization process can bring it down to the required amounts and tonal response for the medium being calibrated. Linearization would have solved it and also produced a more useable negative.
If there is time in the future have them stabilize their darkroom so that any negative produces the same results on any given day.
- Start them by sending a piece of unprinted OHP Ultra to use in a step exposure test for them to determine first useable dMax exposure. The OHP absorbs UV and that needs to be part of the exposure test. The first useable dMax exposure time (or units) will be their standard exposure time.
- Then print out the 16x21 target and have them return a carbon print to you for measurement.
- Use that resulting curve to reprint the 16x21 target and send them that for the 2nd iteration.
- When you measure that it usually produces the final curve which will then produce calibrated negatives to their carbon process.
- If you notice anomalies at that point it is usually due to darkroom process being unstable. You cannot over-emphasize that they must be able to get the same results on any given day from the same negative if they intend to calibrate the process (goes for the film and darkroom - but darkroom first!)
Rachel
IJM-TechSupport