Quote Originally Posted by sanking

To avoid any misundersteanding the SBR/time values I gave for both the 2;2:100 and 1:1:100 dilution of Procat-HD were based on UV readings, not blue channel. That is because I am testing for kallitype and palladium printing which are sensitive primarily to UV light.

In general I would need to substract about log 0.30 from my UV reading to approximate the blue reading. So in effect if your readings are giving you a density range of 1.6 with the blue channel reading this would be an effective DR of 1.9 or more for me with a UV reading. Did you check the results with your X-Rite 361 in UV mode?

As I have indicated my density readings were taken with an Xrite 310 densitometer (does not have a UV channel). I initially read the reflection densities of the Stouffer tablet exposures on Azo grade two and grade three. From that I was able to gain the ES of the paper. I then tested to gain an equivalent DR on my negatives by again exposing a Stouffer tablet and reading the negative densities through the blue channel.

I had emailed you with the results of my reflection testing and you provided me with the 1.60 DR based upon my step tablet readings for Azo grade two. We had decided that probably the UV readings were not applicable when one exposes the Azo with a 300 watt reflector flood (I imagine that this source is very low in UV output). I believe that you indicated that while Azo's primary spectral response lies in near band UV it will expose to visible light in the blue spectrum. Apparently that is what occurs with the reflector floods that are widely used by Azo printers.

I don't know of anyone that is exposing Azo with a UV source since the exposure times are generally acknowledged as being too short to be manageable. I did find yesterday that I will be able to drop back to a 150 watt reflector flood since my exposures ranged from 6 to 11 seconds with the 300 watt reflector flood lamp. I acknowledge that this is a further indication of the beneficial lack of general stain with Pyrocat developer.

I think that the type of light source and amount of UV output may very well be the basis for the discrepency that you seem to question.