Alex Hawley said:
Great stuff Don and thanks. Thanks to PE too for the additional explanation.
Since I have never done any densitomer testing, I have two questions:
(1) what does the numerical spread in the values mean? Is it a large difference between papers or a small difference. Just at face value, it looks like a very small difference.
(2) Are the differences between the papers detectable to the eye? Understand this is more subjective, but can the differences really be seen and how apparent are they?
I just recently ran a comparison between Kentmere Bromide (grades 2 and 3) and Azo. No densitomer tests, but to my eyeball, the richness and depth of the deep blacks were indistinguishable.
I have seen spreads like this in the same paper with different levels of gloss due to different polish on the ferrotyping plate. I have seen the same coating with different dmax based on the overcoat and I have also seen dmax vary if you make a print, dry it, measure it, rewet, redry, remeasure and etc. I've seen dmax drop with this procedure from the same sheet of paper. I've also seen it go up with this rewet, redry procedure. It depends on the paper hardness and swell, I'm told.
Here is another test. Make 2 identical prints and place one on top of the other offset left, then repeat offset right and evaluate the dmax and dmin visually, then flip papers and put the bottom on top with the former top paper on the bottom. Do the offset evaluation of dmax and dmin. You will often get a big surprise from the subjective evaluation of how two otherwise identical prints differ just by position (top / bottom and left / right).
This latter effect is due to left and right eye differences and the fact that the paper on the bottom has no additional white backing and therefore 'looks' different to the observer.
These differences can be virtually eliminated by using a MacBeth viewing cabinet with standard light source, and measurments can be done with a spot photometer at about 3 ft distance.
PE