Testing for Paper Contrast Grades

[Neil Poulsen]

How does one test for paper contrast grades, to determine if they're 1, 2, 3, 4, etc.

Is there a reference for this?

 

[Kirk Keyes]

Neil - you can use a step wedge. Make an exposure, enough that you get a good black on the least dense step of the wedge and then measure the steps on a densitometer. There's an exposure range over which you measure the paper's response (I'm afraid I forget what that is right now) to match the ISO specification. See the link to Roger Hicks page below to see what the ISO ranges are for each paper grade.

Keep in mind that the ISO grades are actually exposure ranges, and they are multiplied by 100 to make them easier to write. Grade 2 has an ISO R range of 90-110, which means that the exposure range is 0.90 to 1.10.

"Beyond the Zone System" by Phil Davis is a good resource for this. To see the exposure ranges online, try Roger Hicks' page here:
http://www.rogerandfrances.com/subscription/ps paper grades.html

 

[Kirk Keyes]

Here's a quick and dirty way - with a Stouffer 21 step wedge, the steps are about 0.15 stops apart. That's a 0.15 log density change between each step. If your paper printed with 7 steps from black to white in the print, that is 7 x 0.15 x 100 = 105. That puts in the upper part of the ISO(R) Grade 2 paper range.

 

[Neil Poulsen]

Hey Kirk, Thanks a lot. I'll take a look at this. As I mentioned, I've gotten good results with VC using Gallerie 3 for testing. But, I think that it may be worthwhile to test on VC Warmtone FB. I need to nail down filtration a good 2 or 2.5, though. Actually, that may be no filtration. The Tech paper for VC WT FB states that no filtration yields a grade 2 paper. Neil

 

[dancqu]

To be sure of a maximum black on the first step see
to it that the second step is equally black. You won't
run out of steps as there 21 of them. Dan