Quote Originally Posted by nworth View Post
The article is excellent, and it gives a good methodology for doing an approximate calibration. Since enlargers vary and dichro filters age, it may be quite worthwhile if you do much printing. An important part of this calibration is the introduction of neutral density to keep exposure times for the various contrast grades approximately the same. Most people just use the Ilford suggestions and go from there. But the Ilford suggestions do not include neutral density, so you have to adjust the exposure for every change in contrast. There are a set of suggestions from Kodak out there that do include neutral density. Many people like to make small adjustments in filtration (usually by changing the magenta) to get the contrast just right, but these small adjustments (up to a third of a grade) usually don't affect exposure that much. Finally, it should be noted that VC papers vary a lot, and a given filtration will not give the same contrast on two different kinds of paper. The differences can be enormous. The calibration technique assumes you print (at least mostly) on one kind of paper. If you switch papers, you can use the grades established for your favorite paper as a point of departure for the new paper, but it probably will not behave in quite the same way. Finally, nothing has been said about the correspondence between density ranges and paper grades. There are some differences between manufacturers here as well, despite some more or less standards. Here is a table from an old Kodak B/W Photographic Papers pamphlet (G-1, 9-71GX):

Grade Paper Log Exposure Range Negative Density Range
0 1.40 to 1.70 1.40 or higher
1 1.15 to 1.40 1.20 to 1.40
2 0.95 to 1.15 1.00 to 1.20
3 0.80 to 0.95 0.80 to 1.00
4 0.65 to 0.80 0.60 to 0.80
5 0.50 to 0.65 0.60 or lower
Perhaps we should just look at the picture to assess it?